I have an 88 pickup with a motor out of an 86 4Runner, just swapped motors a few weeks ago and it's been running like a top. Last Thursday on my way to work I noticed it had some trouble getting up a hill on the freeway I hit the hill doing 75 and by the time I reached the top was doing 50 in about a half miles time and not a very big hill being around Kansas City. I can EASE into any gear and take it clear to 5 grand but the moment I pass half throttle it runs like it's getting no air/sputtering and missing. The MAF or AFM depends who I talk to has under 30,000 miles on it but it sat on the 4Runner for about 2.5 years now without running. It has done if for two complete tanks of fuel.
The things I've done: cap and rotor, coil, swapped AFM from my parts truck, plugs wires, checked for vacuum leaks, coolant temp sensor, unplugged the TPS. All with no change.
I'm starting to wonder if both air flow meters have went bad from sitting just don't really wanna spend the money if someone else has had the same issue thanks!

 

Sounds like a fuel flow problem to me. Check the fuel filter and/or the fuel pump.

 

Forgot to mention the fuel filter is new, is there a strater valve on these to check fuel pressure?

 

found my receipt from 3 years ago for one of the MAF sensors got a new one and it's running the same, but my fuel filter that has 4000 miles on it was plugged guess that's what I get for buying stuff that sits all the time