I just finished up my tubo set up on my 65k, 03 sierra z71. It has a t4 t66 turbo, water meth, air to air intercooler, 39lb injectors, and a z06 cam. right now it is putting 406 to the wheels with 8 lbs of boost with 89 octane and I just started to tune. Tomorrow I will be putting 93 octane and 12 lbs of boost to it. my goal is to have my daily driven truck to be dependable and run the quarter in the 12's. my questions are how much horsepower is safe on a 5.3 and how much boost is safe? I will sacrifice power for safety. Should I leave it 406 or should I shoot for about 450 ( my original goal ). What do you guys think? Oh and when I say I just started to tune I don't meen me, I have a professional shop doing it.