skip/sputtering problem!! Tryed everything!!

[1991fordranger]

okay i have a 91 4.0 with 106000 miles, its 4 wheel drive.. but it has a sputter problem mostly in reverse and sometimes on cold mornings when i firsts start it up, but if you floor it, it goes away, so far i have put on new wires and plugs, new fuel filter, and i have cleaned the IAC and the MAF sensor, i have cleaned the manifold, i have run combustion cleaner through the engine, and i have ran sea foam through the brake booster line, i have ran fuel injector cleaner through it too, ive tryed everything, the check engine light has never came on or anything? what can i do to STOP this annoying sputter?

 

[65Ford]

Having similar issues with my 94. What is the SeaFoam trick you mention? How do you do it and what's it supposed to clean? thanks-