At idle it runs rough and I think it's only (or mostly) running on 3 cylinders (1, 3, 5). The only code was a P0300. I can remove any one of the front (2, 4, 6) wires from the plug and it does NOT change (worsen) but removing any one of the back (1, 3, 5) makes it rougher. With the engine off I can even remove all front wires (2, 4, 6) and start it up, it starts and runs the same way if the front wires are connected or not. The ignition module appears to be working properly, I can see and hear spark when I remove the wire(s) from the plug(s). I have changed the plugs, the old ones had a lot of carbon on them.