Originally Posted by kingranch89
No the truck runs fine an shifts well an everything only thing i notice is my mileage is horrible im only gettin like 10 around town an all i have on the truck is 35's with a leveling kit and a banks monster exhaust
If it's acting fine and your building boost decently(you are aren't you?), than my next guess would be maintance stuff. Oil change, filters(both oil and fuel) and your air filter, what about those? How many miles between those being change? Change in fueling habits, get bad fuel somewhere or go to a strange place during your mileage drop? If you have access to a professional scanner see if your pulling a cylinder contribution/balance issue, that would ruin mileage and horsepower for sure. Just wish I had more to work with.