1995 Astro 4.3 V6 engine type w misses when hot 47,000

Its had new fuel pump distributer cap rotor plugs and leads+battery when it starts from cold its fine ticks over nice and revs ok but when get warmed up it misses when braking for a roundabout it sometimes stalls. When pull of lights it starts to miss then clears itself when traveling on motorways at 65 mph it will die you put your foot down no responce 2-3 seconds later it kicks in then flys off very strange no faults in pcm no light on in dash no chevrolet dealers in spain will touch it one put his scanner on it found nothing wrong played with egr valve it tested ok all other valves and emmision sensors all ok. BUT when cold its purfect( I think I should move to the northpole)please anybody HELP ME many thanks mark