Pork, I assume you have done some mods. You have been posting here for quite a while and without going back and reading them I am going to assume you are running some kind of upgrade on your pipes and breather. When you get those mods done, it is always good to also upgrade to a programable ignition module, these are made by HD and 3rd party vendors. If you had your work done at HD they most likely sold you one of theirs. After the techs install your mods they download a new ignition "map" that SHOULD work best with your selected upgrades, on your specific bike. The problem is that the canned maps don't always work very well and you get a spitting, popping, rough running engine that doesn't deliver smooth horsepower through all the gears. As long as you have a programable ignition system, a dyno tuner puts your bike on a dynomometer and runs the engine through all the gears under varying load conditions. I didn't hang around to watch it but they tell me a good dyno test can take a couple of hours to do right. In the end you have a custom ignition map specific to your bike and all the parts on it. When done they will lock the program into your module and give you a backup (thumbdrive) for safekeeping. I took mine to a tuner with great references I got off of this forum. Total cost $400, and the bike runs better than new. In the words of my son "dad your bike is even more awsomer".
Downside to a dyno tune... Don't do it until you have done all your major mods (pipes, breather, ignition module, cylinders, heads, whatever) because if you do something major after your tune, you have to have to have it retuned.