Problem with WUR
 

I have a '81, 911 SC 3.0 (Europe). The problem is that there is no fuel pressure after the WUR. Someone let me borrow a WUR from a '77 or '78 engine just to verified the condition of the WUR. Although, the Porsche is not running perfect at least is running. Can anyone assist me in finding a good rebuilt WUR? Website such as Warm up regulator-Special T Auto has the correct warm up regulator and warm up regulators for all cars - The De Lorean Parts Specialists rebuilt the original WUR. I also read about a digital WUR, but not sure is it worth changing. Thanks