i have bigger tires but i also have a scan gauge driving computer. i did a 100mile each way trip and going i was running 75-90 and got 13. coming back i was cruising 55-65 and got 16.2. i can watch my real time gas milege and above 2,000 rpm it would drop from around 20-25mpg to 15-20mpg. try to keep the rpm between 1500-1800.
and i ahve one question in this topic...if i adjust my big head waste gate to open at higher boost (only about 18-21 now) would it help my millege?