[SolidStateS15]

an exhaust shop can easily fab you up a new Y-Pipe in 2.5" which will help you out a lot. then you can get some small round high flow cats put on it and retain your O2 functionality and emissions. if that's all you need then great, but for 800 you can get a full exhaust front to back which would be the best. even if you get a magnaflow catback system to bolt up yourself it would be better. don't worry about headers. they don't really help much on a 4.7 and you'll lose half your money just on those. the stock headers just happen to flow great on this engine.

if you do have the exhaust shop do a full exhaust then ask about getting a full single 3", with a new 2.5" Y-pipe. i would buy the cats and muffler of your choice elsewhere for much cheaper and just have the shop weld it all up. the 4.7 really likes single 3" though and performs well. the main thing to check for at the shop though is what type of bender they have and how skilled they are. some places just use crappy crush bends like stock which does you no good. it's almost impossible to find a mandrel bender in a shop which would be best, but next up is a press bender which if done correctly can still produce nice bends. i would ask to take a look at some of their work or bends they make to be sure they look good. they should stay mostly round throughout the bend and not look crushed or smaller in the bend than the pipe which makes the restriction. every shop is different and you may need to shop around to find both the quality and price you want to pay. just so you know though, not sure what costs are these days but i had my full true duals welded up for 800 so a single system should be less than that. that's just for the pipe and welding not inc parts i bought.

 

[SolidStateS15]

you won't pass withouth the precats, plus it's illegal so you will fail visual. the O2's will also have issues and throw codes. you can use O2 sims, but they don't always work the best.

you should just leave the factory setup and use high flow replacement precats on a larger dia Y-pipe. be it magnaflow or fabricated.

 

[SolidStateS15]

negative. i just went for emissions last week. all i have is headers, Y-pipe, and a magnaflow muffler. no cats anywhere on my setup. CT emissions has no visual inspection anymore on newer vehicles. the only thing they do is plug their scanner into your vehicles port under the steering wheel and then you're done.

you have a completely different engine and setup. does not count. you shouldn't just remove the precats and leave all 4 O2's in the system. it's going to screw up the A/F mixtures. it's a lot different than just having 1 O2.

it doesn't hurt to have them in there. either buy the correct magnaflow Y-pipe with precats or have a shop make you one for probably less.

 

[SolidStateS15]

yes late 00 to 01+ have 4 O2's and 3 cats(2 precat and 1 downstream). i don't know many 4.7's running no cats and if they are it's not a good idea. 3rd cat removal is no problem, but the precats should remain and be replaced with high flows. i guess if you had a really clean engine it may be possible to pass the sniffer test, but i wouldn't count on it. if all they use is a scanner to read the O2's then it would probably be easier.
if you never plan on leaving CT then you could maybe at least pass for there, but not many other places. most do a visual along with the emissions testing, or just a visual + safety inspection and you won't pass.

it's not that hard to pop in a couple high flows though just to be safe.