Maybe I'm wrong but it seems like my gas mileage is getting worse. I have a 07 Yukon with a Black Bear Tune Airaid Jr. intake and Magnaflow muffler. The Black Bear tune has disabled the active fuel management and stays in V8 mode. My mileage around town is under 13 and highway is around 16. Does this sound right or is it low. If it is low how can I get it back up. I'm seriously considering putting my factory tune back in.