1988 T/A w/5.0 TPI Auto trans. Hypertech chip with low temp (170) thermostat. modified MAF, SLP headers, crane roller compu-cam, Pete Jackson gear drive, MSD box, coil and billet distributor.

The car ran good until about a month ago until one day, out of the clear blue sky, the motor would run for about 3-4 minutes and just when you thought the motor was coming up to temperature it would lose all spark and die. No matter what you do the car will not start for about 4-5 days. Then when you go out to the garage after the 4-5 days it will start up and do it again. It does set a code 42 but I am not convinced that is the problem. I have replaced the ECM and checked all the wiring going to the ecm and even went so far as to substitute the stock distributor when it dies and still have the problem. I also have disconnected the MSD box and went back to the original distributor setup, including swapping a new coil. If anybody has a clue as to what the problem may be please do not hesitate to contact me. I am completely stumped and have no idea where do go from here. Thanks for your time & help!!
Pete Olson: confused:

 

Have you checked your wires and plugs? You didn't mention if you did or didn't.