[Walt Fricke]

Plus - is the frequency valve buzzing/clicking palpably? It should do that at idle as well as at any other RPM, so it is easy to check with your hand.

Rereading, I see you have the pressure gauge for checking control pressure. At least I think you do - you just called it a fuel pressure gauge. If it connects in line between the FD and the WUR, and has a valve, that's the pressure gauge needed. List your cold and hot control pressures, as well as your system pressure. Those are the figures the CIS gurus always ask for, and with good reason.