Just test them yourself....set up a mock fuel system. It's not like they're doing much more than simple measurements with the proper equipment. Making sure the injector sprays nicely is done with eyesight and bright lights, fuel flow is measured as volume in a specific time frame.

I didn't do that mod, but I did set up a makeshift injector test rig for a different purpose. It's not as exact as the company you'd pay $200 for the service, but as long as you pay attention i'd imagine the numbers wouldn't be too far off.