Synyster

Misfire detected in Cylinder 3, 4, and multiple misfires detected.

Thinking of replacing the plugs (don't know if previous owner ever did this). What else could it be. Possibly injectors? Maybe the IAC?

Bustedback

Most likely in the ignition system. Replace the spark plugs and inspect the boots for any signs of the spark leaking out. If the plugs are worn and the gap is too big it will put a lot of stress on the boots. Electricity takes the path of least resistance and will jump to the easiest ground if the plugs are shot and the boots are bad. The IAC has nothing to do with spark or misfires, it only maintains the desired idle speen depending on conditions of how much load is on the engine at idle. I doubt it's an injector problem, they don't fail as much as people think they do.