I have had Lennie's sprockets in 3 bikes (11S, 12GS) now and can only attest to their usefulness... just installed a set on my friends bike yesterday... he was blown away.
As for the FRK... I believe in tune-ability and as such, the Techlusion/Dobeck/Wunderlich FI tool is what I deem best and have always used in conjunction with the sprockets... open your pipe a tad and add a free flowing air filter and voila!
If you want smooth and responsive... THAT is the way to go... you increase torque and bring it about 1000 RPM lower across the whole band.
Both the Booster plug and the FRK seem to fall into the category of "Resistance Tuning"... they cheat the engine into thinking that it is colder than it actually is and as such, force it to run richer... it works, but it's a "blanket statement" approach...
Been there - already forgot about it...!
Follow my Journey, pursue insanity: