I need help with my loss of MPG after timing belt replacement.

What is your question?

I was getting 37 mpg in town and 48 mpg on the highway, I had the timing belt replaced as well as the water pump, the transmission fluid and filter done and the oil changed and new fuel filter. The car has 112,000 on it. After the all the work was completed, I noticed right away that my average mpg dropped, I'm now getting only 37 to 40 on the Highway and between 27 to 35 around town. I took the car back to the dealer and they checked the timing and said it's ok. I'm wondering if the belt maybe off by one tooth, the VW service manager said if it was I would know by the car running real rough? Could the tech be missing something, could the belt be off? No check engine lite has come on, at 40 mph when you step on the pedal it sounds like the timing is retarded. If anyone knows what the problem maybe, please advise!