Vapor lock I travel 100 miles one way once every week or so. Average speed 67 miles on divided highway. Last month after traveling approx. 90 miles, my 1999 Subaru Forester (150,000 miles) started losing speed, then accelerating again, then losing...etc. it did this twice, with about a quarter mile of normal speed in between. I pulled over and turned off the car, thinking that I had let my gas level get too low and I was running out. It was 97 degrees outside and I was running the AC. I had it towed to my regular service station and they couldn't find anything wrong, plus I was not out of gas, but was very low. Since then I have been using the car only for small in town trips. Then yesterday I got on the highway again and after about 50 miles of traveling about 67mph, with AC on (86 degrees outside), suddenly it started acting up again. Not as dramatically, but it seemed that if I tried to accelerate over 60, the engine sounded very rough. I slowed down and took the slower roads home, because after a while, after I was stopped at a light, my car took forever to come up to even 40 mph. ( Sorry that this is taking forever). I stayed behind a large truck because his gear shifting was about as slow as my acceleration abilities, and after about 15 miles of stop and go driving my car went back to feeling normal and I went the rest of the way home with no problems. This morning I took it to a local station and he checked my fluids and put it on the computer and everything was fine. My husband mentioned vapor lock. Any ideas? I have to drive that same route tomorrow so my husband is going to follow me. Anything I should do differently?