I was wondering if I could use COBB Stage 2 map with just a catback and hi-flow cat and keep the stock downpipe(I also have a AEM intake)? If not what HFC to use I want quiet? Are there any one piece downpipe/HFC cat combos that are quiet I see Invidia has a one. Had one on my STI and that worked well. Thanks.

 

Ultimate Racing, ETS, and I am sure a couple others sell 3" hi flow cats that should work well. Your stage 2 might work okay with that set up, but I would really put a down pipe as well, particularily if you are considering a one piece down pipe cat assy. The downside with that option is that when the cat goes, you have a downpipe to replace, in addition to the cat. I prefer the UR downpipe, or the ETS style tubulars over the AMS downpipe. The reason is simply that the AMS down pipe, while the quality it top notch all the way, is pretty heavy. I will say though after installing an AMS down pipe for a friend of mine, that their downpipe will likely out last the car by a century or two.

 

Agree with Kozmic27. Do replace the stock downpipe (you can leave on the stock O2 housing) - it's pretty easy and they're not very expensive.

 

If you are not going to do a full turbo back exhaust do not put the stage 2 map on. spooling and boost levels may not operate correctly.

Use the stage 1 map. You will squeeze a little more power and keep it relatively stock like you seem to want to.

 

You can always buy a test pipe and bring to a fab shop and have them make weld on a resonator for quietness. Thats what I did to mine and brought it to Akuma Motorsports in NJ. They do great work there at a good price.

 

I don't agree with this statement. I've read many threads and seen quite a few dyno sheets showing the stock DP flows just as well as an aftermarket DP, when the stock O2 housing & stock turbo are used. Waste of time and money just swapping out the DP without changing out the O2 housing as well.

The main restriction is from the cat, not the DP.

I am currently running a Perrin CBE, AMS HFC, stock DP & O2 housing, AEM CAI, and the Cobb Stage 2 tune (for the AEM intake & with the boost pill removed) for at least 6 months now...the car runs mint and I've haven't seen any CEL's yet.

 

darwin is right on, the bulk of the restriction is from the cat. and his car sounds awesome. if you do use the stage 2, i would do dyno pulls, 0-60, or logs to prove you gain more power over a stage 1. my car feels stronger on a stage 1 tune over a stage 2. the logs and dyno pulls confirm this. the car has a megan cb with the baffles removes from the tips.

 

Thanks for the info. I too believe that the stock cat is where most of the restriction is and will probably do the HFC first and see how it runs and sounds. First I have to figure out why my car last night went into limp mode and threw a CEL. I never had any issues before with the COBB stage 1 AEM map before. Thanks again.