Hi David, my heart goes out to you. I too have a late series Ace V8 bought by a previous owner from AC Cars just after the Frimley fire, and finished privately (DE1102). The blueprinted niche line 4.6L quadcam ran like a bag of nails, poor starting, stalling in traffic, pinking, flat spots, stalling on the over run; horrible! Like you, in the absence of any OBD outputs I set about renewing various things (TPS, Idle valve, EGR and DPFE sensor, COPS and plugs, temp and lambda sensors, in-tank fuel pump etc etc). The last place I looked was the ECU. When I did, I found my car fitted with an aftermarket unit by British company 'DTA Fast'. It's an S80PRO unit. They sold me a USB cable for a laptop hook up and I downloaded their software and manuals for free. I found that my ECU had only a rudimentary set of values in the ignition and fuel maps and no refinements such as over run fuel cut off. Just about enough to get the engine to run. After much experimentation, I now have the engine running like a dream and ready for a final tune up by the professionals on a rolling road. In hindsight (!) I wished I'd looked at the ECU first before amassing a whole load of spare parts. I don't know if my story is relevant to your situation but a look in that direction is highly recommended. Best of luck and I hope you solve your problems one day soon!