I will be THE MOST GRATEFULL PERSON ON EARTH FOR THIS QUESTION TO GET ANSWERED

Trying to be detailed without being confusing.
This truck was purchased a week ago and while the engine was warmed up well, I test drove it and it ran almost perfect. I bought it. The next day when it was cold it seemed to idle down to a point where it would sometimes cut out. During driving, after depressing the gas pedal there would be a second or two delay before the accelerator would engage almost throwing you back in your seat every time. If the gas pedal was depressed too much, it would have an even longer delay and might not accelerate at all. I had to learn to drive it w/ the quirks to get to work a couple days. I then had help to change out all of the spark plug wires, plugs, cap and rotor all of which needed attention badly, I also was advised to change the fuel pump. After doing so, the engine RAN AND STILL RUNS GREAT. But. ? IM NOT SURE WHAT IT ACTUALLY MADE RUN BETTER? "That makes almost no sense I know" but why I say that is, it basicly only left me with the problem of having the 2-3 second delary in acceleration when the gas pedal was pushed but when it acutually accelerated it was smoothe and powerfull. And it didn't seem to cut oout when it idles down so low. When it truck is good an warmed up; it is sometimes not even evident there is anything wrong with it. But after being cold? Forget about it. Regardless of cold or hot, the engine just has a major delay from time gas pedal is depressed to the time it actually accelerates and then jolting you back in the seat caue all that gas is finally igniting or something? Not sure. "Again", if the pedal is depressed too much it only makes the delay even longer but usually will cause it not to respond at all.

I can't afford a mechanic and am making wishes upon gods at 2carpros!