My RPMs aren't fluctuating enough to show on the tachometer, but it is enough to feel. It happens lower than 42 MPH as well, around town if I go up a hill anywhere from 35-40 it will happen as well. Seems to be worse when more weight (the family) is in the car, so I'm thinking it's engine related. I'll try a new MAF sensor since I have one laying around, then I'll replace the supercharger gasket. Is there any procedure to setting the BBV? I would really like to rule that out as a suspect.