AT WITS END!!!!

82 Ford Bronco 460 Efi with a spark issue.
It starts cold fine, runs for no longer than about 2 mins then cuts outs, stops dead. From that point there is no spark whatsoever. Almost like something warms and stops operating. We have changed coils , distributors and ignition modules with no difference to this problem until its cold again.
Any Ideas or suggestions (other than setting fire to it) would be welcomed.

DINAMITE!
The only thing left that i can think of might either the brain box on the fender well or posiblly the points maybe your not getting the timing right? sounds like at this point any thing is worth trying