Got her all apart and found cylinder #3 injector cup leaking and head gasket for cylinders 6 and 8 both blown! Not too bad of a job pulling heads for never doing it before. took me and my brother 9 hours. The head gaskets we pulled off were .040 thousandths of an inch. Does that make it a "C" gasket?

 

Got Her back together and the truck runs great! I'm getting better fuel mileage and a ton more power. There is no programmer on it but it feels like it has a lot more power than it should. How can I tell if the computer had been tampered with prior to me owning it. I am definatly not complaining!

 

with out knowing the prior history it is difficult to tell. there is no signatures or info that is stored on the ECM other then (correct me if i am wrong) reflash counts

if you are concerned you could always have a dealer flash it with the stock GM tune and then go from there with a new tuner