The 3.4 is a bit of a dog to make performance mods to - its not nearly as simple as if you had the 3.8. Saying that, the mods that would really give you power tend to be a little expensive.
A good cat back exhaust system is a good first place to start - reducing the exhaust back pressure will be worth a decent bump in power across your whole powerband and make the 3.4 sound a little more husky. On top of that, if you have a stick shift, you can consider a cold-air kit. That will give you 4-5 hp by reducing inlet restriction. If you have an automatic, it won't do much of anything, since your trans will shift before the engine really gets up to the point where the CAI makes power. However, if you really want to try it, its not a terribly expensive bit to add.
Finally, get yourself on the fourth gen f-body forums and look for the 3.4 mods they suggest. There might be a few tricks that are hiding in the forum posts there.