Don't know why the idle changed but it won't be because of the exhaust change .
There's an idle adjuster screw on the left side of the bike . Look between the frame and panels near the throttle body for a phillips heads screw.
Australia might be the only country that had the restrictor to comply with the learner approved power to weight restrictions. Go into diagnostic mode on the dash and see what your throttle reading goes up to. Restricted was 70%
You need to machine your FZ6r cam gears to fit the FZ6 cams.
It changes the power band from pulling between 6500 - 10000rpm to being 4000rpm to 11000rpm