Since we are dealing with an open loop EFI the computer has no idea what is going on with the motorcycle exhaust so it cannot compensate for lean or rich conditions. The EFI is much like a 1985 Chevy throttle body in it's technology. The Power Commander (PC) allows you to alter the timing (PCIII-PCIIIR) and the fuel mixture as needed to tune your particular combination. There are programs called "maps" that can be downloaded into the PC. There are many maps and more being developed constantly. These maps are developed from motorcycles running specific combinations of parts. For example, a Screaming Eagle air cleaner motorcycle part, mufflers and stage I ECM upgrade. These maps are usually all that is needed to get the EFI running spot on. Fine tuning, changes to the maps can be done via a connection to a PC/Lap top and the Power Commander software. If you desire a map specific to your setup or, there is no map for your setup you can have the motorcycle tuned on a Dyno-Jet Dynamometer. This will allow the operator to fine tune your air- fuel mixture and timing-advance curves Powercommander is working on a program that we will most likely be able to download, from their website, that will move the rev limiter to 6200....so you won't have to pay for the harley one. He said it will be on powercommander.com when it is finished.