i commented out a
console.log(touch.pageX);
and now the performance in FF seems to be much more smoother? can it be? it did not even get executed? strange.
It's now fast for a few seconds, then gets slow shortly after the footer loads.
after a long hard fight i made it faster (overall but especially in FF) .... the CanvasPixelArray Object (which is not an Array in Webkit ....) is a real bastard.