I have a 243k mile 1990 12valve stock except for 93 IC setup, turned fuel pin, 1/8" timing advance of pump, half screw of smoke screw, TF727 4x4 w/3.09s for A/R I am running 10mpg trans is tight and nothing seems to drag, no blue or white smoke at idle was getting 20 average mpg at 70mph, but horrible Mileage lately like down to 10mpg! and im not doing the heavy go-pedal, just keeping her mid way to floor at cruising, and the k&n airfilter has been cleaned

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Still getting 10mpg on a 325mi trip, no leaks new filters, almost thinking it might be cheaper to drive my old 77 440 w200 dodge if this keeps up

 

I wonder what kind of fuel pressure the ip is seeing. Insufficient fuel supply caused be something such as a clogged filter or week lift pump can cause weird issues. As can a crack in a line that allows air to enter before the lift pump. Just in case Ur wondering, just because a crack lets air in doesn't automatically mean it has to let fuel leak out. I had that happen to am a long time ago on my truck. Had me baffled till it finally got bad enough to leak fuel.

 

Im starting to wonder, it was acting like fuel starvation before when i first bought it so i got a new lift pump, and stopped studdering under accel, but holy crap! 10mpg, i have been tracing and checking, i know something isnt right, even checked turbo its a peach, i am just going to breakdown and find a pressure fitting and a gauge to boot, if all worst fear i hope IP isnt going out