Brian,
The pair valve removed is just taken off and the holes blocked.
It doesn't do much excpet get it out of the way and keep the bike from backfiring during decelleration.
The Pair MOD is when you route one of the hoses to the crank case vent and cause a vacuum within the crank case. That helps the rings seal better on the cylinder wall.
It's been used in drag racing for years.
If those pros do it, you can bet it helps.
I have it done on my bike, but thats just me. I want every
1 hp that I can get!
Is it worth taking the bike down to do? NO.
If your body is already off?
Sure, why not?
If the motor is fresh, you might see 1-2 hp.
My Buddy has like 16,000 hard miles and it made 3 hp on his.
Back to back, removing and reinstalling it, 3 times with dyno pulls to back up his findings.
It might be because his rings are a little loose and they could use the help that the vacuum offers?
?
Hope this helps.
Chris