I installed the cv tuners kit on my FXDX during the Winter and it greatly improved the performance of my bike. I bought the bike last December and the only upgrade the previous owner had made was to replace the exhaust with Screaming Eagle slip on mufflers. I added a K & N air filter when I rejected the carburetor. I received an email advertising the V-Ductor and since it was on sale it was a no brainer. The immediately noticeable improvement was quicker warm up on starting, smoother acceleration and deceleration and a better sounding bike. I'll be back to report any other improvements after putting some miles on the bike with this upgrade.