Just changed my spark plgs to ac delcos, changed spark plug wires, changed optispark and put on a msd blaster coil with new wire and my car is backfiring. I know I put the wires on the opti correct and on the spark plugs correct what else could it be.

 

my car backfired even when it was stock, just cuz it was running a little rich. did u gap the plugs before u put them in?

 

Im guessing you have an lt1 then? Its pretty random, but once when I had my oil changed they put too much oil in, and that made it backfire REAL interesting like at a cold start, blew my whole air intake off once, that was an interesting night.
Anyway, I drained almost 9 quarts of oil the next day, and it never back fired again.

 

9 quarts!!? thats enough to force it around rings and foul all your plugs up. actually happened to a buddy's mustang when he had the wrong dipstick in his car and went over by about a gallon

 

oh sorry the car is a lt1. It runs ok but bogged a little and never did it again. I even changed the water pump, I know that has nothing to do with the ignition system but I just hate the idea of me having to trace down this problem from scratch or start tearing things down again. Yes the plugs were gapped.

So far
1. new msd ignition coil
2. New optispark
3. New plugs that were gapped correctly
4. new wires that were connected correctly.
5. New headgaskets and im gasket. no air leaks

Ok that narrows it down some what else could it be?