Ah right so its already got a modified breather system. Yeah try disconnecting it, but keep the pipe high just incase theres any oil in it otherwise you'll make a mess lol (shouldnt be though), ive still yet to find something to permenantly block mine (currently blocked with a 1/2"-1/4" reducer socket )

Well the fuel pressure can be checked by depressing the metering head, leave it over night, and before turning the key or anything, remove the air filter and gently push the flap down, should have a little resistance and move down smoothly, and when you let go it should rise slowly and smoothly, if the fuel pressure has gone it will spring back instantly and bounce a little bit at the top.