Got a 97 lariat with a 4.6. When I got the truck I was getting 16mpg on the highway. Here recently it has gone to crap at maybe 12mpg highway... got a tune up with plugs and wires and filters and all that... but got no response in mileage. Anybody have an idea about wht the problem with the engine or computer or whatever is? Please help!
Thanks in advance

 

Clean the MAF -

http://www.fordf150.net/howto/clean-...low-sensor.php

And clean the TB -

http://www.fordf150.net/howto/throttlebodyclean.php