Hi im newish here. I am currently working on modding my grand prix gtp and plan on initially going down to a 3.4 to 3.6 pulley. i know i need an intake, throttle body, exhaust heads, plugs, coolant elbows, tstat, and a few other things including a tune. i know you need these things for a 3.6 to 3.4 set up. my question is what are the best exhaust heads for the car for the 3.4 and eventually going to a 3.1. i only want to do it once but if i have to do it twice i wouldn't be mad.