[Cooter0003]

On my 83 suburban 4x4 with a 350, I’m having light/medium throttle back firing issues, I’ve tried everything. Timing is at 12 degrees initial, 38 total I’ve got 18 inches of vacuum at idle float bowls are set right as best as I can tell, it’s a Holley 4160, I can’t figure this out it’s driving me nuts. What y’alls opinion??