Originally Posted by Dr. G
Power comes from the removal of the cats. Look at the turbos when you remove your downpipes and you'll realize where the real bottleneck on the exhaust side of the system is.
I ran 1/4 miles with 3" and 2.5" downpipes back to back multiple times and could not pickup any difference whatsoever. The times were always identical between the two.
Sounds promising to me, cause i was afraid of low hp gains,because of 2.5 xi pipes