How to make sure that your WUR is faulty? 

The only way to test your warm up regulator is measuring the control pressure. If the engine is cold, the control pressure has to be low, around 0,5-1,5 bar. (You can find the accurate values in repair manual for your car). But with warm engine the control pressure has to rise to around 3,5-4 bar. If you can not observe correct values, although the fuel system supply pressure is correct, your WUR definitely needs a fix.