The microfueler reads engine RPMs in addition to manifold pressure. It's function can be tested with a couple of wires, a bulb and a resistor. David Fulcher explained how to do it a long time ago to me when I was having some trouble. I don't remember what type of resistor was required. I would think your standard fuel injector test gear, although more expensive than the aforementioned method, would do just fine. Why are they guessing at this? Are they not capable of determining if a fuel injector is actually being activated? I don't get it. :confused
I do know the company that originally made them which was based in MA is out of business.
BTW - Have they installed the AFPR and what is the pressure at idle with the vacuum line off? It should be about 48psi.