We had a similar problem with our '93 850 with 110K mi. Check the torque arm bushing - the little rubber bushing in the arm over the engine that keeps it from rocking forward and backward. Ours was shot and apparently the rocking back and forth (upon braking/acceleration) split holes in both the vacuum hose and the big air intake hose (not sure what it's called exactly) between air filter and throttle body.

The car would run fine in upper rpms, but run rough and die on return to idle rpm. It also had trouble starting.

both the bushing and the hose repairs were easy do-it-yourselfer fixes, but the old bushing had to be cut with a Sawzall before it would come loose. Replace the bushing with polyurethane from your favorite parts source (Trollhatten, IPD, etc.) as the OEM bushing is inadequate.

Hope this helps.