Anyone out there with a Z20 and a 225 ETEC? What kind of gas mileage do you get. I have a 2005 Z20 and a 225ETEC HO and i am getting no where near the gas mileage that is advertized. At 4,000 rpms i get about 2.5 miles per gallon. I should be getting better than 4 miles per gallon based off the ETEC advertising.