Not trying to hijack, but I have gotten the chance to analyze some injector cleaning machines, and I may start kitting the electronic portion together soon along with a shopping list if anyone wants to build their own. It will operate exactly the same as the high dollar units... which pulse an injector at an adjustable frequency, pump fluid through at different pressures based on the injector, and measure the output. Some shops also use ultrasonic cleaning for scale and residue, which isn't a bad idea either.