MYSTERY PROBELM?? To all the mechanic Gods out there in cyber land; I beg of you to SAVE MY SANITY

I bought the truck almost two months ago from an individual. Guy was able to get me because of the fact that "IF THE TRUCK HAS BEEN DRIVEN ENOUGH" to have it really wamred up; the problem almost isn't even there for a while.
I have done some things twice and both times with mechanics that, along with myself, was convinced that the truck riddle had finally been solved. Then the nxt morning after it was cold again it would continue with this;

starts and idles up and down while in park. Put in drive and push the gas pedal and NOTHING happens for maybe 1-3 seconds when, instantly the truck takes off almost spinning a wheel with the release. Its "seems" like it must be getting some kind of gas while the pedal is depressed cause every once in a while there is a "mini" backfire before it will take off.

I first changed the plug wires, rotor, plugs, dist cap, and fuel pump. "The existing fuel filster seems to be having been just replaced.

then for that evening it ran perfect. Till the nxt morning and it started giving delay again.

later, I checked the timing and it was almost 10deg off and there was two fairly significant vaccume leaks that got taken care of. Then; RAN REALLY DAMN good all night long! Till next morning.
NOW, MECHANIC GODS out there; I will be forever truly in debited to you if some answer to this MYSTERY problem I seem to be dealing with.

btw, the odometer meter apparently has been disactivated I guess intentionally and the temp guage has been destroyed as to prevent the driver from seeing if there is over heating; even though there hasn't seemed to have been any overheating considering water has stayed same level.. "Just throwing that out there" all the info I can thnk of for now guess.

anybody following my pain and mave answer for relief?