[ALipper]

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.

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.

 

[ALipper]

how do you keep the O2 sensr from throwin a code? Mabe I need to go where you go.....

buy piping with 02 bungs welded in. then all you have to do is pop the 02 sensor in.

 

[ALipper]

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.

i bought the truck with the current setup. i think my truck only has 3 o2 sensors from the factory though. i believe 01 + have 4 sensors. correct me if i'm wrong. this is why i want to change my exhaust setup in the near future.

 

[ALipper]

thing is, most guys on here run without any cats.

 

[ALipper]

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.

i don't plan on leaving CT, but like i said all newer vehicles (i don't know the cutoff year), they only plug their scanner in the module below the steering wheel, let it sit for a few minutes, and you're done.