Every time I've had a misfiring it's been the coil packs or the spark plug wires. There are two ignition coil packs and two spark plug wires. I would replace all of those things first. Idk if the Sport20 has an OBD-II port, but read your manual to find out. If it does, go get a code reader from Autozone and see if you have any codes. Who said you blew the C339G integrated circuit on the ECU? Is it obviously melted? It should be a little black box with "C339G" printed on it.