Newbie

I have a 2004 grand prix gtp, I took it in for a tune and everything come to find out that my #1 cylinder is readind 60 psi, and #3 clyinder is reading 70 psi and #5 cylinder is reasding 120 psi this a supercharge car as well. The check engine light is on and want go out. I just bought the car fom a auction and the technican tells me two things could be wrong with it either burnt valves or head gasket issues. Keep in mind the car is not running hot. Can anyone tell me whats really wrong with it?