While working on grill heard fryer popping. Popping coming from center vat. Removed combustion blower and ignitors. Found right side ignitor damaged. Pilot tube almost gone. Inspected burners for cracks and found none. Replaced ignitor and started unit. Heard another pop on first ignition. Lowered manifold pressure to 3.1"wc. Let unit heat and heard no more popping. Unit heating normally and ok at this time.