Are you talking about the BG 44K, or about the actual BG Injector Service Kit?
The 44K just goes in your fuel tank (insure that you're about full on the tank, it's not the concentration, but the length of time in the fuel system).
The Injector Service Kit disables your fuel pump nd runs the vehicle off of the injector cleaner only, about 15-20 minutes. This insures that the injectors are cycling with a heavy duty cleaner in them.
Either one will work, but the Service Kit offers instant satisfaction, with a noticeable driveability response (if the injectors were dirty enough to be noticeable). The 44K also works, but is less noticeable, as it happens over the time period of burning a full tank of gas.