The stethoscope and water sound like great ideas. I was thinking about how spraying a fluid would effect the idle. I wouldn't be surprised if when the fluid finds the vacuum leak it temporarily "seals' the leak, thus briefly returning the engine to it's normal idle. Water and a stethoscope sound pretty safe too.
Smoke and ultrasonics sound cool, but out the budget range of this amateur
Thanks guys for all the great tips. When I'm done with my ball joints I'm going to inspect both my E's for vacuum leaks. I'll first try the stethoscope and then the water. Once I've found any leaks I'll try an assortment of chemicals/gasses to see if there's any difference from water. I also will tap into my O2 sensor to see if an amateur like me can notice any difference. I do know that my O2 sensor (and my duty cycles on X11) are all across the board. Would it help to disable the computer or plug any of the ancillary vacuum connections? Has anybody found any readily-available plugs to cap-off the vacuum lines while diagnosing?
Thanks!
Robert