I need help what cuases exhaust backfire in the morning on my 1987 K5 Blazer. Here a list of what I've done so far. Brand new MSD distributor, MSD Spark plug wires, MSD coil, checked timing, Magnaflow highflow cat converter, Flowmater cat back system, engine bored .30 over, compu cam camshaft, jet chip computer, throttle body spacer from CFM Tech and adjustable fuel pressure regulator set to 13 psi. I also check the computer for trouble codes and found no errors. All of this started happening last September. Is this normal for an old truck? I bought this truck last summer and everything was running fine, until I started doing all of this upgrades. I begining to wonder if if was worth it. Please help me figure this mess out. It's quite embarassing with the neighbors in the morning when it backfires. If backfires about three to four times when the engine runs for about a minute or so. Please I need some expert advise!!!