Aprilia RS125 Italkit Pneumatic Power Valve
ITALKIT version of the Rave 2 valve but simpler and cheaper.
It is a Pneumatic valve that opens up around 7800 - 8000 Rpm which is just about the perfect timing.
Like the Rave 2 you will need to drill a hole in the cylinder to allow the exhaust gases to open the valve.
There is an instruction sheet included in the kit.