My concorde is a 3.7 liter with a 140,00. It runs fine around town and on back roads at 55 mph, Then when taken on highway at 70 mph after 26.6 miles it dies and will start again after about an hour. The cam shaft, crank and map sensors have all been replaced. Engined was flushed and still doing this. Every mechanic I talk to is at a loss. No one can figure this out. Any ideas????? PLEASE HELP