OK Percy, I didn't want to go in this direction from "my unique experience", but it seems you have covered all electrical bases. When I got my DJ, it had a strange miss and pop no matter what I did for tuning. When I removed the engine and took it apart, I found "open cracks" at the flanges of the intake mounts, letting in air to the shared cylinder out of sync. PO not only cracked the flanges, but did a 'bubba weld attempt' that was not solving anything. Maybe that 'crack potential' is something to check for on yours? Good Luck.