Howdy All! I am hopping you can help me diagnose this. My brothers boat seems to be popping out the exhaust between 3800 and 4200 RPM's or so. You put the pedal to the floor and it will push past the popping to cruise at 4800 RPM's (Pump Probably Getting Loose =) without as much as a hiccup. It was fine when we put it away from a day at the lake, then next time we took it out it popped. Since it started, New Cap, New Rotor, New Plugs, New Wires, New Coil. This last time it ran, past Saturday at Modesto, I re-gapped the plugs from .045 to .037/36 with no change. The plugs did look cleaner towards the back of the engine while the the ones near the front were darker. Thoughts on where I should start?
Stats: 79' Nordic Bubble Deck, Stock 454, Air Gap Intake, HEI, Vacuum Holley 750, Stock Dominator Pump, OT Headers.