Here's the deal. I got an the hi power (cat back) and and the HKS down pipe. My question is should I get a 3'' or 2.5" test pipe/hi flow cat? Because I believe the HKS is 2.7" all around. Which setup do you think would yield the most power?

Thanks in advance for your help,
Josh

 

get a 3inch. I have a hi power also with the down pipe. The part on the cat back bottle necks where it connects to the cat. I think its 2.9 . The part that bottle neck is about the size of the regular pipe. maybe a little bigger. Its not the best but it looks and sounds official. I also have a 3inch ultimate racing test pipe. Take the cat out believe me you will feel the difference. Oh yeah only for offroad use do you take the cat out, umm yeah.