First off, this thing makes the throttle response tremendously better! I am very happy with this addition. I also added an FMF Fatty pipe at the same time. I used the jetting specs that came with the pipe and I'm loving the broadened power band and crisp throttle response.
I was worried that the installation on my 2000 YZ125 would be difficult, as I heard that the case would need to be modified to add the Vforce3 reed block. The installation was much easier than anticipated as that is not the modification that is needed!
The modification is actually to the carburetor joint. The kit includes some gaskets, fasteners, and instructions. There are provided washers that are used to act as a spacer between the reed block and the carburetor joint for the modification. Then it calls for the use of a hack saw to cut the tabs off the carburetor joint (as pictured below) in the space opened by the washer. Then you disassemble and clean out the debris, and button it up with the gaskets. Simple!
pictured is a representation of the required mod; red lines are lines to cut (this is a rough sketch I know)