Volvo Repair: 1989 740 Turbo Wagon Transmission, I think, rubber hoses, flagstaff arizona

Question
Recently we drove from Flagstaff, Arizona to Los Angeles.  On the way back, while halfway up Cajon Pass the car slowed down to a stop.  My son's car towed us to the summit.  There, we drove it around on level ground.  While in Park or Neutral the engine would rev as normal; but when we drove it on level ground it would not exceed 20 mph, and would not go up hill at all.  We've had the car towed back home and are trying to consider a plan of attack.  Prior to this incident there had been no indication of any developing problem.

Answer
Mike, since its a turbo, I would first check all the basics like the rubber hoses and perhaps it may be a faulty air mass meter.  This sort of thing requires testing of components and without looking at the car, I would only be guessing on things.  Have it checked out by a Volvo Shop. Roger