I have a 1990 454ss truck that i recently bought, the truck was sitting for 6yrs. I Replaced water pump, all water hoses, intake gaskets, egr valve, distributor, cap and rotor, sparkplugs, sparkplug wires, two injectors and cleaned tbi. The truck has lost of power and backfires from the tbi when driving. When checked for timing, The mark on the balancer moves up and down. I checked for compression and it's good 145psi on 6 cylinders and 150psi on two cylinders. The guy that i bought the truck from told me that somebody had replaced the cam. Iam starting to think maybe there's a flat cam lobe, or the cam is to radical causing the knock sensor to not work properly. I need help.... Thanks
SAL