I was looking in my manual today and have noticed that it shows a vacuum switch valve which is situated under the petrol tank and is connected to the rocker cover via 2 rubber pipes and also to th 2 inner pipes off the inlet manifold and also the bottom of the air box.... Is this standard on all zx6r G1 models because mine does not have this..... the rocker pipes are joined together and the others are blanked off, I only noticed this after I got a new/ 2nd hand air box and the pipe was on it....... only asking as I do have this flat spot and wondered if this could have something to do with it...its shown on page 47 of the manual downloaded off the manual web site and is item 4...... :azq