Thought I'd throw this in too- The added bodywork accounts for a loss of 3+ MPG on the freeway.
Just clocked 54,000 on the oh eight and it gets worse mileage than either of my GT's. Even my auto got better mileage!
Exactly what kind of mileage are you getting?! I average 26.2 with mine. That accounts for city and highway. I've even checked it using the "old fill er up, set the trip, divide by the miles/gallons at the next re-fill" and the computer is pretty accurate plus or minus about 0.5 MPG.