I'm not 100% behind the O2 sensor being bad. I'm pretty sure there would be a CEL if it was. It would need to be pretty bad to affect driveability as Steve describes.

I'm tending to think more along lines of some swapped vac lines. If he swapped the ones between the FPR and the Charcoal canister... (Steve, see yer PM)... that could possibly (probably?) cause his symptoms.

Steve, yes, for measuring the manifold vacuum, you would need a vacuum gauge. Not overly expensive, but see if you can borrow one from someone first. It _is_ a useful tool, but unless yer needing it all the time, might not be worth buying one (maybe $25 or so). I think you might be better off spending the bucks on a dash mounted gauge, then you can constantly monitor it. And, believe it or not, a dash mounted gauge can help increase your gas mileage! When you see that needle hit zero every time you jump on the gas, you begin to realize that you could accelerate a little less! (mine has increased my gas mileage about .3 MPG! from about 17.1 MPG to 17.4 MPG, measured over 600 mile span... Big whoop... but it was FREE!)

Hope you get it sussed!