Mac hi flow cats ... Hp ?

This is going to sound weird but the truth. Back in 1997 in the state of Florida we still had emission testing. My car at the time did not have heads and cam yet (Edelbrock Intake, 70MM TB, Headers, Pulley's, etc.). I ran a 2.5" MAC high flow catted H-Pipe and also ran a MAC off road H-Pipe. After emission testing I'd put the off road on. Anyway there was a local dyno day and at the time I had the high flow catted pipe on the car, it made 241HP / 292TQ. I went home and installed the off road pipe, went back to the dyno, it made 237HP / 289TQ. The catted pipe made more HP and TQ. This is on a 240HP though. I sold the pipe after the emission testing was no longer in Florida.

I think it'll quiet down the car a bit. Since you're making some serious HP it may rob some power. It's undetermined how much until you dyno it.