My 1985 Volvo 740GLE suffers from an intermitten failure to accelerate when asking for more torque from the engine. It doesn't happen all the time and I have had it at the shop twice. My mechanics are volvo specialists here in town. They did a lot of testing of the fuel system and they replaced the air mass meter with a new Bosch meter and told me that all the tune up parts are OK. I had to take it back cause the problem was still there. They now tell me that there is carbon deposits in my fuel system and put a commercial grade fuel cleaner in it. I ran the car with the cleaner in it and the problem is still there. They also suggest that the throttle body should be cleaned. Will cleaning the throttle body make a difference or is ther something else wrong and was it necessary to replace the air mass meter? The car did have a recent tune-up and fuel filter change and air filter. The car has 145,000 miles on it. Any suggestions???