Is there a gain replacing the muffler on my stock catback?

I was thinking of replacing my stock muffler with something better, Is there a direct replacment that I could get some gains from?

Not much of a gain.. Maybe a couple Hp.

The hooker Aerochamber claims to be adaptable to the stock catback.
http://www.texas-speed.com/shop/item.asp?itemid=325&catid=46

I'd think that most of your gain in a complete catback system would be from replacing the stock muffler. The intermediate pipe really isn't that bad, but the stock muffler is pretty restrictive. There's a lot of different stock replacement mufflers out there, depending on the sound you're looking for.

It also depends on if you still want tips, kuz you can get some nice single in/out mufflers at a decent price.

I think camaro's and formula's look amazing without any tips

Replacing the stock muffler alone will net close to 10 horsepower. The stock pipes are not that restrictive. The intermediate pipe is 2.75" and the muffler outlet pipes are 2.5" each. The cross-flow muffler is restrictive.

Magnaflow or Dynomax.