Originally Posted by 944Ross

Are you running a K&N type (oiled gauze) air filter? If so you might check to see if the AFM is gummed up on the vane seals. I had that happen on a VW, the added weight of oil and the dust it collected threw things way off.

I have a bone stock car and at 70, at mile high altitudes, A/C on, with lots of big hills, I get 27. On the plains I regularly see 30+ at the same speed. Can you put the stock tune back in and see if it improves?