Ok, If you have a 3 in DP, a 3 in hi flow cat and a HKS 30th Anniversary exhaust, how do you mount it? The reason i ask is, the HKS tapers to 2.65in to meet the stock cat, so how would you connect the exhaust to the cat? If anyone has this setup please let me know. Thanks

 

anyone? someone has to have a setup like this.

 

The flanges meet just fine. Should not be a problem. The pipe tapers a bit, but the flange is still just as big as a 3" pipe flange.

I have my 3" Helix HF cat mounted to my HKS catback. The Helix flange is slightly larger than the HKS, but the holes line up and the gasket seals fine. No leaks.