Here's the link to the test/repair procedure for the WUR
http://www.landsharkoz.com/tt/ttwur.htm i know its for a 928 but the operating principle is the same..yours won't have a vac input
...They work by increasing the fuel pressure (via the galleries in the metering head)..at cold and as the bi-metal elem,ent heats up it backs of the fuel pressure off to normal.
If you bypass it and do a few stone cold starts and the engine starts ok, then its suspect.
The bosch book is to big a task to scan all of it !! i can do a few pages at a time. Let me know what you need /
cheers