Power gain from high-flow cat and muffler

Thinking of putting an aftermarket performance muffler as well as a high-flow cat on my 99 v6 GA.

Now, considering I leave the rest of the exhaust system stock, what kind of power gain am I looking at from the new muffler? What about the catalytic? Is it even worth putting the cat on?


Thanks

Seems a lot of guys say around 5% + gain. Better with headers. High-flow cat. is a must, biggest power drain.

Yeah, I agree. The cat will cause the biggest drain and when yo u go to hig flow version you'll notice it for sure.

Watch out, though, there may be a "downside" 02 sensor on the original cat., or some other sensor, so replace. cat will have to accomadate the sensors.