I've not heard of anyone having to do this when fitting a new exhaust unless they
are having the bike dyno'ed,
fitting a wideband O2 sensor ( Autotune)
or reducing excessive popping on deceleration.
The PAIR valve ( I assume this is what you are referring to )allows fresh air into the exhaust gas to ignite unburnt fuel, the cause of the popping, it will also confuse the O2 sensor as it will think the bike is running lean, hence why it is blocked off during a dyno run or fitting a wideband sensor.
Cant answer if the block off plates from a Blade will fit a CB1Kr but the same result can be obtained by blocking the pipe that feeds the PAIR valve from the airbox. It can also be done without having to remove the tank and other gubbins.
See viewtopic.php?f=62&t=10395&st=0&sk=t&sd=a&start=40 for pictures. The pipe can be blocked by inserting a normal sized marble. I pinched in the marble with 2 zip ties to ensure there was no way it would move.