If you have stored your car for awhile and then run it hard, chances are you may have damanaged your plugs electrodes. Pull the plugs and ensure the gap is within spec. My Explorer had a terrible miss at a certain RPM and it turned out that a gap adjustment of only .005 inches (from .055" to .050") fixed the problem. If it's a miss, it can only be 1 of 3 things, or a combination of the three. Fuel, Air or Spark. IACV could be the culprit, but I doubt it. Besides, checking/adjusting spark plug gap is free, and a new IACV isn't. Before making any changes though, run your gas down to nothing and then fill up with good quality gas. If the plugs are gapped properly, I would turn to the next cheapest item in line .. a fuel filter. If it's a stumble more than a miss, it could be the fuel pump. I would only fork over the dough for a new IACV if it was a last resort.
