Would going to 2.5" from beginning to the end be okay for my stock setup? I don't think I will be upgrading the ECU but would like to get better low end torque and a less turbo lag with my stock ECU. Would this custom made exhaust cause any problems with the ECU and cause some weird error codes?

Or should I just go with 2.25" downtube and 2.5" catback or just a 2.5 catback?

I've got the ATR 2.5 down pipe and cat but stock exhaust. That alone made a noticeable difference. I also have a SAM chip, K&N, and use DurAlt for a combustion enhancer. I am a little skeptical of the HP claims of the exhaust. For a lot less dough, you could have a shop fab you an exhaust and muffler setup. $695 is ridiculous. I am sure, however, that it is excellent quality.

Good Luck,

X

Unless money is tight, I'd go for a full 2.5" exhaust with 2.5" downpipe. Just go custom - you'll end up saving a lot over a bolt-on one from IPD or Supersprint. The ECU won't throw you any codes provided the exhaust is made and installed properly.