hey my 1997 f150 2wd with a 5.4l triton motor has 267,xxx miles on it. the only things that ever needed replaced were the alternator and coil packs. i put an insys usa intake on it and true dual 2.5" glasspacks. it ran great for about a month and i got between 18 and 20 mpg. and now it seems less snappy and i get 14mpg no matter what. this truck is crazy reliable and the frame and body are spotless. i need help on getting my economy and power back so i dont have to sell it. thanks
I would take that intake off, clean the MAF, and see if that doesn't take care of it. Not sure what kind of filter your new intake uses, but oil based filters are known to cause problems with MAF contamination.
Plugs haven't been changed in a while only because they are a bear to change. MAF sensor is fine and the intake is spottless. My filter does not use oil. I was thinking more along the lines of plugged up cats but Idk.