1990 oldmobile 98 164k miles 6 cyl eng

Starts fine when cold runs good. While its warming up it misfires if hammered but if babied drives like a dream. After driving for a 20 to 30 mins it just stops running. No misfires or slow power down shut stops running and wont start again till after it has had a chance to cool. Not so much as a pop or ping. Replaced inginition pack and control module spark plugs and wires. When warm it will turn over but its a no fire. Please help.