I drop a 1/4 splash of Berryman's B12 in the Wife's Ninja (FI), rest of the bottle goes to my other ZRX (carbed).
Seems to help the ZRX run better after sitting all Winter (drained the bowls, fill both w/ 91 non ethanol fuel).
Couple rides, they're fine.
Many different brands out there, basically all "try" to do the same thing.
"snake oils" my buddy with the Honda Goldwing calls them.