Backfire through Throttle Body on 1989 MJ

[DJ'S MJ]

I have a 1989 MJ. Rebuilt the engine. Now 9.4 to 1, Stage 2 cam, 58 mm TB, Pacesetter Header, 19 lb 4-hole injectors, and ported & polished head. At Idle, runs great and sounds even better through Thrush muffler. Accelerate and it backfires through TB?? Any one out there has a clue what to do?

[1989commanche]

Sounds like timing

[Warren Mohler]

are all intake valves seating proper? push rods too long, valve springs weak, was cam "broken in". How does it start. timing, how long since rebuild, any miles, has it done this from initial start up?