Test Pipes - What type of performance gains?

[lnferno]

I searched the forums and found a few people ask this question already, but without any good answers.

I'm Stage 3, APR downpipes w/Twin 2. How much improvement would I see by putting on test pipes? Ideally, I'd like someone with experience post some measurable gain (i.e. dyno, FATS, logging, etc).

TIA.

[Paulyworld1432]

Also just thinking about this today.

[joeS407]

test pipes not much extra but it helps breath at high rpm, youd be better off getting a different cat back the the twin 2 with the 2 mufflers is pretty restrictive, maybe think about a full custom exhaust just stright pipes tubo back, the whole sysetm would cost less than a set of awe or apr down pipes with test pipes

[highPSI-S4]

There was a thread awhile ago about it. (months ago). The answer was the main cats are not restrictive enough to have huge gains by removing them. Thats why on most if not all aftermarket Downpipes, the precat is the main concern. If the main cat was as restrictive as the precat then it would make sense to swap it out for a test pipe. all test pipes do for are cars is make more noise. I'm not stage 3 but i've been that route, I do however like the sound. Maybe on a bigger setup like GT's the main cats become more of a flow factor, just not on k04's.