Engine revving up and down (Saab 9000 CSE 5spd)

What vintage is this 9000? If it isn't the hoses, the next thought would be the Idle Air Control (IAC) valve - a bit more expensive than a few feet of hose.

Good luck.

Walt Kienzle ( snipped-for-privacy@core.com) gurgled happily, sounding much like they were saying :

It's worth taking the IAC off and giving it a damn good clean out with an aerosol of carb cleaner - worked wonders on my 900 with similar variable idle speeds.

Check all hoses. Symptoms sounds very much like a vacuum leak. There is a small 2cm hose on back of manifold for extraction of crankcase fumes. The end might well be split. Look also under to hose. I have repaired this twice on my 1993 9000 CSE. First time i could cut off an inch of hose. Second time I cut off an inch again, but fitted a small new hose section with a stud to old hose.