I am wanting to put an exhuast on my AP2 but dont know what a good choice would be. I was thinking of an invidia cat back then eventually getting the headers and test pipe to match.

 

There's a thread about this already, on the same page as this one.

NEway, I had an Invidia on my first S2K. It had a good sound, but was just really loud at all times and was just totally annoying to live with. That was WITH the silencers. With the silencers you could hear the car 2 blocks away. It had a good sound, but I wouldn't buy another (my first S2K was rear-ended, mangling the Invidia).

I have a CT Engineering one now. It has a deep sound, but during cruising doesn't really make much sound. The Invidia just always droned.

 

Search much.

For power, go with a single that is as big as possible.