For some reason I am getting worse gas mileage on the highway. I have a d15b with the proper ecu, intake and headers. In the city I get 33-36 mpg but on the highway I only get about 26mpg. The only thing I can think of is aerodynamics. I currently done have the fender wheel liners in so it is all open. Any ideas? Also I usually drive about 75 on the highway.