yes you should do the reomval of the pair valve. It is a valve that pulls air out of your airbox and injects the cean air into the exhaust port so that it delutes the exaust air coming out of your bike. Leaving it will cause you to have backfire problems. It is also some unneeded weight. Not much but still unneeded weight. You will need to also get a block off kit to do it. Check this site for some more info.
http://home.tiscali.nl/hayabusaclubh.../mod_pair.html