try to verify first , is it a fuel , or ignition fault, run a meter off the fuel pump see if its losing voltage , that will help to rule out its not the fuel pump relay,, run a meter on both pumps positive lead, next if the overvoltage relay is old just replace it there very common to fail, it powers up a lot of componants, next check ignition if its cis has and ignition module they fail when hot, your going to need to monitor the coil and see if when it stalls there is or is not spark, on an older car 560 sl i found my ezl was shutting down signal from fuel relay to ezl ie the signal voltage signal was lost when hot and if i remember i replace the ezl