I dunno, I trust my cruise control more than my right foot. It seems to stay under 5 inches of mercury once I'm at speed, and its very very good at keeping the car at speed. It almost never deviates from 10 inches of mercury while cruising on a flat stretch. When I cruise however, the fluctuations are much more noticeable and I often hit 0 inches or go into boost. My instantaneous MPG on the MFD is also significantly higher with CC on than with it off, which is probably because the car is much more predictable when its driving itself.