http://www.wot-tech.com awesome selection and many options on alot of things
http://www.milzymotorsports.com another good place to buy engine parts and the elusive ported 3400 exhaust manifolds
http://www.zzperformance.com some toys but not much for a 3400. look under grand-am and a few intake parts are under grand prix
http://www.wbodystore.com lots of replacement parts
http://www.getoverkilled.ca pcm option
http://www.intense-racing.com pcm option and future 3400 parts