my 2000 rs has a sort of buck problem too. every now and then when i down shift and go for it she bucks. but when i let off the gas and go for it again it's fine. could this be a fuel issue?not yet.as the car sits at work 45 minutes away from me,and with all the stuff I have got going on,I haven't been able to do much more than guesswork,and I have no scan tool to use either. Am going to pull some sensors off the obs that are interchangable and test them.