Thanks again, guys. As an electronics tech, and not an auto electrician, I have replaced ALL the caps in the ECU, and the fusible resistor going to the relevant CEL output pin was open circuit. I checked again today having opened up the ECU and plugging it into the vehicle, and once again, there was absolutely no output from the CEL or MIL as it is called in the manual. I have tested, as has the mechanic, had all engine sensors either checked or replaced, (bit of a fishing expedition, apparently), and as I said in an earlier post, a couple of auto electricians that just made things worse. The car will start and run fine, rev to the red line, for as long as it feels like, and as soon as you actually put it into gear and try and drive it, it just dies in the butt, won't rev, stalls etc. I still think it's the ECU, but I will double check 361UZ's suggestion, as that helps.
Gloverman, apparently the owner wants the car to remain as is, with this motor, so what would it cost for a known good refurbed ECU. I know you can't give a warranty on a secondhand unit, so that is up to the customer.