the flat spot sounds like an air leak. The fins on the intercooler will make no difference to your problem. The fault code will tell you there is a problem in a system but not always the component that is faulty. If you have the same codes with the new ecu then you can eliminate the ecu. I am afraid that trying to do this on your own is going to be damn near impossible unless you know your diagnostics. I would say you need a specialist as well. Maybe someone from here can help you out. to me it sounds like more than one fault, maybe fuelling, plus air leak plus maybe an electrical problem. Good luck.