But the question still remains:
why is the throttle plate closing early?
Is it an engine-saving measure, so that the cylinders don't get starved for air b/c the air can't flow fast enough to get the proper amount into each cylinder quickly enough at those high RPMs? (b/c the higher the revs, the less time there is for the cylinder to fill with the right amount of air before the valve closes). As I'm just speculating, that's only my off-the-cuff WAG.
Btw, @
jamesm, welcome back
.