these are common problems that I have seen/heard of.... -Look underneath the car! I remember a guy that bought a Z and later looks underneath to find that it had been all dented up from a speedbump or something. -Check to see if the stock antenna works -Down shift from 5th to 4th and listen for grinds, also from 3rd to 4th at high rpms. -Open up the rear hatch and look underneath the latch spoiler for any rust. -Let it sit for awhile running idle, watch for any smoke coming out of exhaust. After it has been sitting for awhile, check underneath for any leaks from Engine/Tranny/Diff. -Have a buddy ride behind you to see if it is smoking under boost.