hello all, i have an 05 screw lariat 5.4 w/flowmastrer cat back dual w/70 series(had the 40 series and was much to loud,sounded like a 69 ss camaro with headers!!!) i noticed after i installed the cat back that my gas milage went south, way south!, anyone else expierence this too? it seems like the 5.4 likes a little back pressure, my gas milage went up a little after i switched to the 70 series, btw i am running a diablo performance tune w/ k&n stock air filter too. maybe there are some settings i need to change on the diablo tunner to get the gas milage back????? any sugestions would be greatly appreciated!!

thanks!!
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I believe the problem lies with the rate, and frequency of the throttle blade opening.

In other words, the problem is probably that you have your foot in the pedal more. Try to conciously drive nice, and see if your mileage goes up. I bet it does.

 

try letting off the loud pedal

 

these guys have hit the nail straight on the head !! it happens to all of us.... with some time, you will drive as you did before, but for now isnt it nice to hear yourself ???