Fuel Injector Cleaning Problem! Help!

I have a 1987 Trans Am GTA 350 TPI. The #6 and #2 injectors weren't pulsing like the others and the engine had a slight miss so I had a friend clean the injectors. We hooked it up and everything and as soon as we go to crank the engine so it'll clean the injectors, the cleaning canister is empty. I dont know how it drains so fast. We disconnected the fuel feed and return lines, disconnected the fuel pump connecter at the rear diff, hooked the fuel injector cleaner (OTC Part # 7448) to the schrader valve, and as soon as we cranked the engine to get it to run off the gas/cleaner mixture, the canister was empty. We dont know how it drains so quickly..in a matter of seconds! We tried it 3 times and got the same result everytime! Any suggestions as to what could cause it? Could one of the injectors be COMPLETELY stuck open and the fuel just goes right through it with no pulse?