Oldsmobile/Buick Repair: 3.8 with a rough idle, vacuum leak, cam sensor

Question
i have a 92 park ave. with a 3.8. the engine idles very rough, but is very smooth going down the road. the OBD shows no trouble codes. have tried to search for a vacuum leak but not sure of an effective way to do this. thought about replacing the AIC motor, but want to eliminate any simple solutions before spending that $65.00....the cam sensor has recently been replaced along with all 3 coil packs and has had a tune-up within the past 4 months. Any help would be appreciated....Thank You.

Answer
hi john,well the way we test for vac leaks is very effective but very dangerous.and a lot of caution must be used,as in this can cause a fire or explosion.but try this,take a spray bottle with soap and water and spray along intake and base gaskets all places where a vac leak could be.if this finds a leak the eng will idle up momentarilly,as to seal the leak. another possibility tap on the egr valve see if eng smooths out if so bad egr.and yes iac motor is also a possibility.good luck please vote for me billymac