Are you talking about the deeper noise you can hear ? If so, mine is the same and pretty much all RS250 Upwards sound the same that I have heard...
I get a weird high pitched grinding sound from my rs250, exactly between 2500 and 3000rpm. I'm suspecting dephaser pulley, but thats a complete guess!
Better clip now Just want to make sure if it's normal or not, this has kept me from going to trackdays last month, afraid something might fail..