Ha! And duurrrrrr....

Forgot I hadn't rechecked CO after rebuilding the top end a few weeks ago. Was reading minus figures on the CO meter. Wound the screws out a bit, which made it worse. Wound them all the way back in until they stopped, and CO went to 1.2% ish which isn't too bad. This has now stopped the near stalling, so it was probably running way too rich.

Anyhoos, seems to be fixed now. Be interesting to see if theres an improvement to mileage, was only getting about 270 out of a tank.