I tried the stuff 2 months ago. There didn't seem to be any noticeable difference, before/after. Maybe my injectors were already clean. For ~$10 a bottle you can't really go wrong. I think your supposed to use it once a year.
You don't put in into the tank. Here's what I did.
Buy 5/16 " fuel line hose (1 feet) and some golf tees.
Prepare for a slight diesel spill.
Disconnect the hose that feeds into pre-filter. Prepare to stick a clean golf tee into it (the hose) as soon as possible. Disconnect the main fuel return line ( the big one leaving the main fuel filter) at the firewall, plug the open end with a golf tee. Or you could detach the line at the main filter and add a foot of hose that you bought. Attach the 5/16 " (the accessory one you bought) hose into the prefilter, it pops on easily and stays there. Plug the open end of the hose you just attached. You should now have 3 hoses hanging around, the main fuel entry plugged at opposing ends and the main fuel exit, also plugged. Pour the diesel purge into a jar. Place the jar somewhere where the diesel rattle won't spill it. Unplug your two hoses and place them into the jar, way into the bottom. Pump the hand pump (white handle beside pre-filter, twist and then pump) until you see the red diesel purge in the clear pre-filter and you feel distinct pressure. Double check to make sure your jar is in a good tight spot. Start the engine and run varying rpm until you run out of diesel purge. Should take around 20 min. Reverse procedure
If you try it please post any results if any.