Just the other day, it started idleing really rough, and when I gave it gas, it would hesitate. Once I got moving, it would go, but every time I hit a stop light, it would take me a while to get going. Took it to a Volvo specialist who said they checked everything out and thought it was the LH control unit. I got two control units from a volvo used parts place, one off a '94 turbo, which would not allow the car to start at all when installed, and one off a '90, which made my car do the same thing it was doing with the original control unti. So I put mine back and am now at a loss since I know very little about cars. I'm gonna replace the air filter just in case. My dad wonders if it might be the turbo; when I accelerate with the car in park to 5000 rpms, the turbo needle doesn't go into the white. Does the turbo only kick in if the car is actually driving? Or would it kick in even if the car was in park and I was accelerating? The exhaust is stinky and black. Also, after the car ran for about 5 minutes and reached normal temperature, it started ideling smoother. If I pressed on the gas, it would still hesitate for just a second but would then rev up. Can anyone offer some suggestions? Any help would be much appreciated!!

by the way, the last time I was having problems with the fuel system in Sept., they repleaced the O2 sensor with no luck and ended up putting it back on and replacing the AMM with a rebuilt one, which solved the problem. Can't remember exactly what the symptoms were. The car has 178,500 miles on it. The check engine light is on, but I haven't read the codes yet. Will do that tomorrow. Help!!!