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Discussion Starter #1
I am having my local exhaust shop install new mufflers in a few weeks, but I am wondering if I should go a little further. I am in WA state

With headers, which ones are smog-legal and do any of them mount without mods to the fender wells? It's possible they all clar fine, but my only header experience is with 70's muscle cars, which usualy require some cutting for clearance...

I had first suggested areal dual exhaust system, but they kind of talked me out of it, based on a large jump in price to do that. As far as I can tell, it would be another cat, but that's it, right? What about wiring? Would it really be a huge deal to include O2 sensors where there were none before?

While on the subject of cats, what are some popular high-flow ones?

Now, this truck is a daily driver/work truck. It's my baby, and I am going to start upgrading at some point or another, probably going to shows, but is a full on system like maybe overkill?

I was reading about the cat-simm, is that smog legal? I can't imagine it would be. I just don't want to put a ton of cash into this and have it illegal in the end...
 

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OK you can run the Gibson headers and you will be fine, now you were asking about adding a second cat, and O2, well the cat would not be a problem, but the computer is not ment to read more that the amount of O2's that came on the truck from the factory. You can not just wire in extra O2 sensors and have the truck run right. If you want the headers that is fine, but I would just run them into a Y-pipe and a high flow cat, single pipe in to one muffler and then 2 pipes coming out the back of the truck. Now I will tell you this, some of the guy on the Mustang board that i'm on have put high flow cats on there car and did not pass the smog test. The O2 simmulators are made to go where the post cat O2 sensors went to make the computer think that there is still a cat there and not ture on the check engine light. I really hope this helps.
 

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I guess I should just listen to what my exhaust guy says, then. I trust him, been using him for years, I just wanted to be able to say "true dual exhaust" :bow:

Do the Gibsons directly replace the stock manifold? Or if I go with them after I get the exhaust done, will they have to rework the pipe after the headers to make them fit?
 
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I dont know about the 4.7ltrs but im looking into a true dual setup from gsmotorsports.com and from what i understand there headers with highflow cats/xpipe and mufflers are totally smog legal and will give a nice jump in power with no cutting or anything to make fit. I guess i will go look at there site and see if they even do anything for 4.7 but i dont see why it wouldnt be smog legal as long as your running cats.
 

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The only thing I can think of with the true duals being a problem is that, like mentioned, the computer cannot read an extra O2 sensor, which would mean that one of the sides will not be monitered by the computer. If that side happened to be running rich, and they choose to test that pipe, you would have some trouble making it pass.
 

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BlackDak said:
The only thing I can think of with the true duals being a problem is that, like mentioned, the computer cannot read an extra O2 sensor, which would mean that one of the sides will not be monitered by the computer. If that side happened to be running rich, and they choose to test that pipe, you would have some trouble making it pass.
Youre 01 should already have four 02 sensors. 1 at the end of each manifold and 1 at the end of each pre-cat.
THe GSM kit w/o cats came with 2 bungs for 02 sensors. So I had to have the local exhaust shop install another pair of bungs for the second set of 02 sensors.
Without an 02 simm box though you will get a check engine light. I had already had problems with stuff setting the check engine light off so when I put in my Nu Image gauges I just covered the bulb with black tape.
 

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So then do the Gibsons have O2 bungs already?

I have two O2's in the manifolds and two at the pre-cats. There is the main cat downline, is there no O2 there? If not, then what would it matter if the pipes split and went on to duals after the pre-cats, but I left the original cat and had another one installed in the new, second pipe? If it doesn't watch the main cat, that should work, right? The two main cats would ensure a clean smog test, and all the original sensors would still be reading what they are supposed to be reading.

Am I missing something?
 

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BlackDak said:
So then do the Gibsons have O2 bungs already?

I have two O2's in the manifolds and two at the pre-cats. There is the main cat downline, is there no O2 there? If not, then what would it matter if the pipes split and went on to duals after the pre-cats, but I left the original cat and had another one installed in the new, second pipe? If it doesn't watch the main cat, that should work, right? The two main cats would ensure a clean smog test, and all the original sensors would still be reading what they are supposed to be reading.

Am I missing something?
The Gibsons do not have bungs for the 02 sensors. They are located in your exhaust pipes right after the header or manifold.
There is no 02 sensors on or after the main catalytic converter. I think going with a True Dual setup and adding another converter would be the best choice. Or just get a pair of Magnaflow hi-flow converters off Ebay for around $50.00 each and replace the stock converter.







 
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The guys at gsm told me on the phone that they have had no problems at all setting check engine lights off because they have all of the bungs for the o2's in the right places, this is just what i was told i could be wrong.
 

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Spider said:
The guys at gsm told me on the phone that they have had no problems at all setting check engine lights off because they have all of the bungs for the o2's in the right places, this is just what i was told i could be wrong.
Well maybe theyve changed things since I bought mine a few months ago. MY system only had 2 bungs for the 02 sensors. My 01 comes from the factory with 4 bungs for the 4 02 sensors.
Also, the rear 02 sensors monitor the pre cats. If you get the kit without cats you will definately get a check engine light. But im not sure about the kit with the converters.
 

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Sounds like alot of problems just to be able to say it's a real dual exhaust. You're unlikely to see any real performance gains. I would just put on some nice tips with a flowmaster and spend the money somewhere else. Chances are, once you do all this stuff, you'll regret it. These computers are tricky, and once you start fooling with emmissions, and installing simulators to fool the computer, you can run into all sorts of problems. I ran into the same thing while installing off road x-pipe on my mustang. It was too loud, not street legal, and cost a lot of $$$$ that I could have used on a real performance upgrade.
 

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Hmm funny crow. I can feel pretty true power gains from my trues. Grant it, i dont have to have a cat because we dont test emissions around here. But that being said i havent had any problems with my setup. The MIL light is on, but my truck still runs fine, in fact it runs so well that first gear doesnt hook, and second sctratches HARD. I can also tell its faster by the cars i race. And if i could go back and make the decision between a cat back, and true duals, i would say trues every time. I'll make some videos this coming weekend for you guys.
 

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My state doesn't test for emissions either, but your truck is still not street legal. All fifty states require catalytic converters. I wasn't suggesting you were wasting your time, I was just proposing that the time and money and headache involved would discourage me from the switch, unless I was racing all the time.
 

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i had 1 cat and went to two, i just reinsatlled the o2 sensors on the rt side cat. no codes or anything, and my Lt side cat has no o2 sensors.

...just when u get a 2nd cat theres lots of expensive wires there on the Lt side that were safe from the factory, but can easily be burnt up if not relocated due to the introduction of a new cat. :biggthump
 

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Spider said:
I dont know about the 4.7ltrs but im looking into a true dual setup from gsmotorsports.com and from what i understand there headers with highflow cats/xpipe and mufflers are totally smog legal and will give a nice jump in power with no cutting or anything to make fit.
they do make it for the 4.7, and yea its real nice......
but the kit isnt exactly bolt right up, i had to cut and reweld a few things
 

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Damn you put the Header on Backwards.. Oh! you just Moved to the other side.. Nice, wish I could get some. I need someone to Shoot a True Dual Exhaust System so I can see How to do Mine.. They Quit Smog Testing in Florida, That is why I can Breath, But the Cat can Come Off instead of running dual Cats..
 
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