How often should the valves be adjusted on a 2 l type IV engine?

I have seen 3 different intervals specified: 3000, 6000 and 20,000 miles!

Obviously you dont have hydraulic rockers?
Never heard of 20,000 miles
Either 3,000 miles or 5,000 kms

Lube service is every 5000km
Tune up (including tappets) every 10,000km

yeah type one's it is either every 3000 or 6000 miles although most do it at 3000 to be careful. Type 4's dont really drop exhaust valves as often, but i guess it only takes about 5mins to do it :thumb

The Official VW Service Manual advises valve adjustments every 24,000 km for '75 and later VWs to keep the Emission Control System Warranty in effect. (Chapter 9 "Lubrication and Maintenance", Section 3.3)

It also recommends valve adjustments 'can' be done at every 10,000 km. (Chapter 9, Section 4.3)