My 87 740 non-turbo with 250,000 mi, never any major problems, suddenly wants to stall at times. I drive it 20 miles, mostly highway speed, to work early in the morning every day. About 70 degrees. No problem. Smooth as a sewing machine. But, in the afternoon, 90 plus degrees, it starts fine at work, no problem for several miles on secondary road to Interstate, no problem on Interstate, but when I exit the Interstate after about 15 miles at 70mph and try to start after stopping at the end of the exit ramp, it tries to stall and is rough running for the remainder of the trip home, about a mile with one more traffic light stop. One time it died on me and would not restart immediately. After waiting a few minutes, it started back up and seemed to run OK. My Volvo specialist, not dealer, changed the Fuel Pump and Fuel Filter. Made no difference. He is puzzled and so am I. Anyone have any suggestions as to what might be the trouble?