Hey I know this can't be it, but this may spark a thought in someone.
It sounds like what I get in my camaro
Vapor lock, I don't know if its possible on a Fuel Injected car though.
It pretty much is the density of the air and the heat make detonation slow and Vapor builds up to the point that it won't start or what it runs like CRAP.
318I convertible, Dinan Exhaust and performance chip
Roh BMW racing 17's, Dinan Stage 2 suspension system. Pinoeer CD player, pioneer speakers front and rear. Pioneer 400 watt 6 channel amp. and MTX 8" subwoofer.