Not tried the 3M product but Berrymans or a straight shot of Chevron's Techroline (at most auto stores) works well. I'd burn Chevron after that as it has the stuff already in it. An old aviation trick is to use Hoppes # 9 gun solvent, especially when heated and used ultrasonically. It cleans injectors better than than anything else I've used. How do you know they're dirty? Have you checked the spray pattern? It's fairly easy to build a home brew injector cleaner, powered by hand pump (ala Bosch's expensive unit) or compressed air if you have it available.