How long has it been since you replaced your spark plugs and wires? If its been a while, I'd change them before considering the ECU. Its very rare for the ECU to be bad so I'd consider that my final option.
Second what gillela said but given that I've owned both cars, I think I can help you here. It sounds like you need another wastegate actuator as yours maybe stuck open. This would explain why you can't go past 3 lbs boost as its creating a large boost leak. The best way to tell is by removing the vacuum hose leading to the actuator and (with it plugged into the actuator) blow into it. If you can blow into it without any resistance, you've got a bad actuator.
Did you open up your ECU? The problem you're having is really common and it's never been the ECU on this car. If you're dead set on getting one, post in for sale. You can also check out the protege groups on Facebook. They're very active.
Side note. What is the model year and trim of your car? I don't recognize that model number and your ECU looks different from my 02 p5 auto ECU and my manual ECU.
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.
Feedback can be caused by ignition coil problems. This sources says it CAN damage the ECU (PCM), but not that it will. I've never seen that on a protege, but then again you have a sport20. I really think you need to rule out ignition coils and spark plug wires before you replace the ECU.
Use google to find the manual for your car or just look for the OBD-2 port. Use google to find out what it looks like.