I have a 383 with 9 1/2 compression, alum heads, moderate cam. Nothing special. 440 HP. It ran great for 2 years. Engine is 5 years old. 3 years ago, the transmission was replaced and after that the pinging started. It was HORRIBLE at anything over 3000 RPM!! I replaced the plugs with the same (Autolite AR3933). It got much better. It started pinging at 4 grand after that. I tried hotter plugs, colder plugs, different brands, different gaps, different wires, etc. It has not been right since. I have changed the plugs, wires, distributor cap, rotor, coil, etc. The AF ratio is great according to a dyno tune. Even the shop couldn't figure out why is was pinging. The timing is only at 11 degrees initial. When new, it was at 14. The timing curve seems correct. All in is only 32 degress or so. I use 93 octane from different stations to be sure it isn't bad gas. It lately has started to "break up" and run like crap at less than 4000 RPM. Is it possible that the MSD distributor is bad or damaged from the tranny swap? It has a Holley 770 Avenger. Is the carb notorious for issues? Was there a wire pinched when the tranny was replaced? I have tried everything I can think of. I am likely going to ship it to an expert soemwhere. I will NOT go back to the builder of the engine because I had a HORRIBLE experience here in VA. I have a video of its terrible performance. I will post a YouTube link soon. Any ideas???