Kawasaki came out with the "pair" system in 1979. I don't remember exactly when i started utilizing it as a crancase evac system, prolly bout 25+ years ago.
Having my dyno since 1993 we get to experiment with every single new bike we get, and one such experiment is determining if a crankcase evac system based on the pair system is applicable.
We have found some skoots make LESS power utilizing the pair system as a c/case evac than with all the systems hooked up normally. The first skoot that made less shocked the hell outa us, we put everything back to stock, redynoed, got our stock power back. The next step was to determine the vacuum strength present in the main feed hose coming from the switching valve, and lo and behold that's where we found the reason for the power loss. The pair system had very good vacuum strength at idle/low speed, but monitoring the suction thru a dyno run, we felt the suction diminish, and ultimately ceased altogether. Since a crankcase evac system creates a "sealed" crankcase, once the vacuum signal ceased we now had the internal pressure building up in the crankcase, thus the power loss.
It has been well documented that when done right converting the pair system to a crankcase evac system on a Busa works and makes more power...period. The only problem we have found is SOMETIMES the necessity to raise the idle rpm a bit. The very good vacuum created by the pair system at idle is ofsetting what the oil pump is trying to do, pump oil. We have more problems on GSXR1K's than Busa's, and if a skoot has a hi-volume oil pump gear it is a non-issue.
Most skoots that respond to a c/case evac will make between 1-3 H.P. I don't believe i have seen more...yet!!
BTW...my Y2K Busa has over 67,000 miles on it , and had the pair converted into a c/case evac on the first dyno session back in 2000 with about 1000 miles on the skoot.
RACNRAY