Id install a PCIIIusb for the sake of the aftermarket pipe, not so much the K&N...but since you got it....do it for both. Despite what the "experts" on here say, the busa benefits GREATLY from a powercommander with slip ons, especially aggressive ones. Picked up 5 hp with a PAIR mod, PCIIIusb and D and D slip ons with a SMOOTH power curve. All the fuel surges and rich spots are GONE. If your just looking for an aggressive sound but want to maintain low rev ridability, this is the way to go. Also contradictory to what all the "experts" say here, ive heard from VERY reputable tuners that full systems without other engines mods are more of a waste than slip-ons, in terms of $dollars spent per HP gained. Good to know if your pretty sure youll never do any internal mods in the future.