Where do you buy your fuel from? Check the ethanol sticker on the pump.. The more ethanol, the less miles per gallon you are going to get. Clean the MAF, if it is a sensor its likely the rear O2 sensor, 60k is recommended change from Toyota. Overall how does it run? Idle good, throttle response? Have you looked at your plugs? Pull one and check the gap, they do change on the 3.4's after having been run for a time. You mentioned the cone filter. Did you oil it up? Maybe it coated the MAF, maybe it has too much oil on it and not letting in enough air..
Originally Posted by spyder041
been getting progressively worse mpg on my truck..1/2 tank is at 115 miles.. Did a tune up and it didnt make a difference.. Can my truck just need to be tuned or something? Only thing I have done is borla cat- back and an open air cone.. Drive like a grandma too..