On a more serious note, just like to document what happened in case it helps someone else.

Bought a new Idle Control Valve at lunchtime, read up on mixture adjustment and X11 testing in the link above and decided I'd have a go myself. Stopped at my local hardware store on the way home and bought a multimeter and long 3mm allen key.

Found the X11 and tested ports 2 and 3, not sure if it would work as my car doesn't have a Lambda valve. Anyway, reading was 2.9 volts against a battery voltage of 13.4, which by my calculation is a duty cycle of 78%. Tried adjusting the mixture 1/4 turn either way but with no discerible difference.

Took the air filter off, changed the ICV, noted that there was a 6v reading at KOEO, which I assume is default 50% cycle.

Anyway, started up and ran great. As I wasn't having any luck with the X11 test readings on mixture, went straight for the carb cleaner method, which worked a charm. Leaned the mixture right off until there was an increase of revs - about one whole turn, I guess - bolted everything back together and went out for a test run. Went like a dream, no hesitation, low idle stalling, rough idle. I am happy, happy, happy!

I reckon I should try the X11 signals again to see if the duty cycle has changed, but don't know how not having a lambda valve would affect this. Would also like to check the fluctuation in voltage on the ICV and maybe even explore the air sensor potentiometer settings with my new multimeter but i'll leave that until the next time I have to take the air filter housing off.

Which I sincerely hope is NEVER EVER AGAIN !!!

Many thanks for the help and suggestions from those who replied to my post and also to the many many previous posters who each have contributed a little more to my understanding of the K Jetronic fuel injection system. If there isn't a book about this extraordinary adventure, there certainly should be.