Ok just out of curiosity..................................

I'm running a catback exhaust system & AMS Test Pipe and I've ran both Cobb Stg 1 and Stg 2 with no issues, well except for the P0420 code they disabled on the Stg 2 map only so when I run Cobb Stg 1 of course my CEL comes even with 2 Anti-foulers installed on my test pipe. But what I don't get is, I've been reading around about how some say downpipe's are sort of worthless unless you get a downpipe w/02 housing and then you see these companies selling full TBE's that are with regular downpipe's. So if you are getting the same gains from a stock downpipe then you are with a aftermarket downpipe then why can't I run Cobb Stg 2 map with just a catback exhaust and have the same peak performance?

Some people say you can. I wouldn't suggest it unless you had at least a A/F gauge so you can make sure you are not too lean.

Some people say you can. I wouldn't suggest it unless you had at least a A/F gauge so you can make sure you are not too lean.
Installing my gauges this weekend, hopefully. :thumbup:

Right on and thanks much for replying. Do you know if this is due to the stock downpipe being slightly bigger then some downpipe's coming with the TBE's?

So if you are getting the same gains from a stock downpipe then you are with a aftermarket downpipe then why can't I run Cobb Stg 2 map with just a catback exhaust and have the same peak performance?


Based on what I have read/seen the CBE is the main restriction in the X's exhaust system. A full TBE will yield better OVERALL gains, but not a huge amount of peak HP/TQ. You will have more TQ and HP lower, and should help smooth out the curve somewhat.

Cobb's newest Stage 1 map allows for a CBE, so I would say to see the full advantages of the Stage 2 map you need to run a TBE, and pull a pill.

Based on what I have read/seen the CBE is the main restriction in the X's exhaust system. A full TBE will yield better OVERALL gains, but not a huge amount of peak HP/TQ. You will have more TQ and HP lower, and should help smooth out the curve somewhat.

Cobb's newest Stage 1 map allows for a CBE, so I would say to see the full advantages of the Stage 2 map you need to run a TBE, and pull a pill.
But that is my question though. My bad for not mentioning this in my initial post but I have a HKS CBE (not stock CBE) and test pipe so all I'm missing from a full on TBE is just the downpipe which is still stock. If you research on downpipes for our cars the way to go is a downpipe with 02 housing (for power) and some companies with the full TBE are only using regular downpipes (little to no power increase over stock - from what I've read) not the downpipe's with 02 housing. So basically what I'm trying to figure out is, is it worth pulling my stock downpipe because I jumped the gun and bought a regular HKS downpipe? I will eventually run a downpipe with 02 housing or just add a 02 dump.

^ Yes I personally think it is worth it, but I guess that depends on your long term plans. I truthfully planned for a long time to only replace the CBE. I now have changed my mind, and will run a full TBE. Not because I think replacing the stock downpipe is a huge deal (because I think it flows well), but basically for future mods (upgraded turbo etc..), and I don't want a bottle neck and would rather take care of it now.

^ Yes I personally think it is worth it, but I guess that depends on your long term plans. I truthfully planned for a long time to only replace the CBE. I now have changed my mind, and will run a full TBE. Not because I think replacing the stock downpipe is a huge deal (because I think it flows well), but basically for future mods (upgraded turbo etc..), and I don't want a bottle neck and would rather take care of it now.
Ok, thanks bro!

A Cobb rep replied on a different forum and said it should be ok to run this type of set up with a their Stg 2 map. :rock:

cool man, good luck with the Stage 2 map!