A KV problem.

[John.]

Excuse the daft questions as I'm a K-jetronic virgin.....although I did have a fling with a 2.8i Capri many years ago.
My recently acquired B3 90 has a running issue;-
Starts off the button when cold although revs a bit high........drives away fine but after running for a few minutes if you try and pull away it dies then kicks back in with a jolt. Once it's hot it seems to be ok but not always.
If you're stationary and you try and hold the revs at say 1500rpm it'll die down to say 1200 and then kick back in up to 200 and then die to 1200 and so forth.
Driving it like this is near on impossible.
........so I took this thing off, see below.(it lives below the air trunking between the airbox and throttle body)


I sprayed it's orifices with carb cleaner and checked the resistance between the two pins, 43.5 ohms. Refitted it but still the same, nevertheless I drove the car and then parked it up for about 20 mins. Tried to restart it but wouldn't fire, I suspect it to be over-fueling so left it for about an hour......then it started but maybe on 3 cylinders so I just kept the revs up till it cleared.
Anyway, I've now disconnected the plug to the above part and it seems to run fine........
......so, what is this bit? Is it at fault?
I haven't tried a cold start yet with it disconnected.
Gonna try and read up on the K-jet stuff but thought I may as well ask here first.

John.