Meant to say on previous post:

I've now ordered a cheap VAG specific diagnostic computer off fleabay (even if it doesn't diagnose the running fault itself, I will at least know when I manage to get the diagnostic socket working) and have ordered a job lot of 3mm silicon tubing so will look at replacing all the vacuum pipes at the weekend and trying to get the diagnostics working. Think I will also be checking the AMM wiring as best I can. Hopefully this will solve matters but we shall see...

Thanks again guys, you're all stars!