Hi,
You should be able to get an RPM signal with just power, ground and VR sensor connected.
Have you got the VR sensor wires on the right way round?
What trigger pattern is the reluctor? 36-1, 60-2,
Have you configured it correctly in MT?
I bought a kit form VEMS and didn't have any problem with RPM signal.
I take it you've built it up as per the build guide?
Cheers,
Gavin