Plug Temp Rating

Plugs have a certain temperature rating correct? What would happen if I were to put the wrong temp rating plugs in my car? Would it cause the cough and sputter under strain, that I have been experiencing for a couple months?

No. Very unlikely.

Does it only do it once warmed up?

nope. Its hard to start, and it coughs and sputters under strain. I had a thread goin bout this before, but never got any responses, so I let it die and went on my own...I'm kinda stumped now as to the problem. Its got new plugs, no vacuum leaks, fuel pressure's fine, new fuel filter, injectors are fine, new intake manifold gaskets...I don't what else to do except pay someone to fix it, and I'm pretty sure that's gonna cost a pretty penny.