A tricky one...

Ok, here it goes.
Got a 1990 H reg Mk1 GTI Convertible. Cold start valve was off when I got it as it apparently caused running problems. Recently tried to fix it and encountered a few problems. Had it tuned yesterday with the cold start valve on and after a juddery start where it needs throttle, it ran 'perfectly' and all CO2 and emissions are fine. A couple of weeks ago I bought a new thermotime switch as it was tested externally and didn't shut off when engine temperature should have disabled it, but it is still showing the symptoms of constant over-enrichment.  Also tested fuel pressure - all fine. When driving normally, then coasting, then back on the throttle, it judders and then seems ok but in genral I would say it feels laboured, like it is running too rich/lean.
Starts and runs fine with the cold start valve disconnected but I want to get it running as it should be.
Any suggestions would be greatly appreciated. The car has not been 100% since day one of me owning it and it's a shame.

Cheers anyone.

have you checked the injectors ie had them out and checked the spay pattern and if they are dribbling? mine had to have new injectors as it was running like a pot pig not cheap to replace but what a difference it made.

yeah. sounds like that would be a good idea. downloaded a good pdf tutorial on injector testing. next weekend will try it then post.
cheers.

ok, did an injector test and a couple of them were a little low. changed them around and it seems to be either the hoses or the metering head. but like i said, the levels weren't substantially different.
next step will be to clean up the WUR. any other ideas?

pumped air through the WUR, replaced injectors, changed tappets (to make sure one of them wan't causing a lag) and it all seems to be tickity boo.