where is the best place to start troubleshooting "missing"? I noticed the car really lost some power then shortly thereafter began to run like a 3 legged horse. On a BBC, I've installed a scattershield and occasionally when starting the car it will make a loud 'bang' noise. Doesn't happen all the time. Also changed to steeper gears, I noticed the temp went up at @15 degrees. It will not start after driving for at least 20min. It'll start after sitting for a bit. Hot start problem?
If your car was running great and then lost power and started running poorly acting like it is missing, with the equipment that you say you have instlled I would assume that this engine (BBC) saw some rpms and I would start with checking the valvetrain (valves, rockers, rushrods). The symptoms sound all too familiar.