i know i need new headers and a y-pipe but would a restictive exhaust cause it to run good at part throttle under 3000 and kinda feel flat when your on it at high rpms? i'm going to put hedman longlubes on and a flowmaster y 2.5 into 3.

 

Your motor is breathign through a straw and it isn't happy about it. Although those headers are slightly better than stock, the rest of your system is holding you back. You have a healthy motor trying to breathe through a system that chokes the stock motor the car came with.