Volvo Repair: 1992 volvo 240 dl engine, volvo 240 dl, volvo service

Question
We drove from NYC to Tampa and the first day was great, engine ran smooth and did 730 miles -no problems. On day 2, engine started to have slight hesitation on accelerating at about 80 mph, this continued to worsen and had same hesitation at 70 then 60, etc. We made it to Tampa (500 miles more) on second day but it not has difficulty when accelerating from start. At idle, the engine seems to run smooth and runs ok at steady speed but is rough and seems like it is "missing" when accelerating.
I had a "check up" before leaving and all checked out OK.
Being far from home, I would like to have an idea of possible issues before going to strange shop for repairs.
You help is appreciated.
Bob Lenney

Answer
Bob, too bad you are about 3 hours away from me.  Im in Fort Myers.  It sounds like a possible air mass meter or a speed sensor.  I would have to check it out.  There was a Shop in Tampa that was pretty good, not sure if he is still there.  Its Dan's Volvo service on Dale Mabry.  Roger