Philip
If you are still diagnosing your problem, then maybe this will help. I had similar symptoms. Rough running below 2000rpm and checklight coming on when took foot off accellerator.
After a lot of checking, replacement of ECU solved the problem.
Simple to check by swapping ECU with known good one to rule this out. Oscilloscope checks showed my ECU sending 4 fuel pulses per rev at <2000rpm and the normal one pulse above that.
Checklight was a false "Over Temp" reading.
nigel
