Welcome.

You're on the right track with headers. If those are your other mods in your sig you got most of the needed mods. Grab some spark plugs and a scan gauge for knock and you should be good to go. Be sure to get a 3.4 specific tune.

Read through this for everything you need to know mod wise:

http://www.grandprixforums.net/safel...car-17482.html