Have you tried putting some injector cleaner in the gas? Others may comment on the following: Haven't tried it myself but maybe try putting 30-40 psi of air pressure into the injector then sticking the end in some water to see if any air is leaking out. I remember someone saying they filled a dirty injector with cleaner, connected it to 12 volts to open it and then used a tube to blow the cleaner through the injector. This seems a little tricky though but they said it did work. You certainly don't want to inhale any cleaner and you don't want a spark igniting any flamable fumes.