I thought a tune-up was supposed to increase fuel mileage,that doesn't seem to be the case with the 2004-2006 f-150s.The company i work for recently had 3 of our 150s,two of them are 6 cylinders the other has 8.I'm not sure how bad the other two are but I drive a 2005 6 cylinder and it lost close to 100 miles per tank.It also lost what little power it had,I can feel it shifting out of o/d more often.I was just wondering if anyone else has had this and if anyone knows why this is?