The "Download" is a remapping of the Electronic Control Module.Which controlseverything from the Air/Fuel Ratio, To the ignition timing. It will alter the A/F Ratio as well as the Timing curve to match the upgraded engine.
You will like the results !!!
i have a buddy with an 07 custom. he just had the same thing done except v/h pipes. he says it made a big difference. to be honest he ran with just the K&N filter and pipes for some time.we talked him into the download in case he hurt his motor. i have no idea what a download is. i got the last of the carbs.
Just did the DL yesterday, had the pipes on for a week and they made the bike sound like a Harley. The stock pipes sounded very rice ish. Lots of popping w/o the DL so I put the AC on and did the DL for $200+, a little expensive but worth it, bike has much more power torque and runs perfect.