Craig --

Two quick thoughts.....

First, a serious leak should make an easily heard "hisssssss", so you could snoop around with a hose in one ear (as a stethoscope) looking for the leak.

Second, an old trick for detecting slight leaks around intake manifold gaskets or injectors is to spray the suspect area with something like carb cleaner or WD40. The liquid temporarily seals the leak and the stumble smoothes out.

I would guess that running rich and a vacuum leak are at opposite ends of the spectrum -- a leak usually implies lean. I seem to remember that the old Bosch FI systems had a common failure of the vacuum sensor causing a rich condition -- perhaps a vacuum leak right at the sensor would have this effect. I'm sure another Brickster can expound.

You should get the manual I sent in a day or two.