I just took my 6 year old daughter to school this morning and I noticed that this "knock" stays constant in its sound whether accelerating or decelerating. It doesn't speed up or slow down it just knocks. It sounds just like a spark knock, a rather sharp spark knock.

On the positive side- since I set the IP timing the engine doesn't miss and hiccup when started in the mornings. I may set the the IP back some maybe to 21deg BTDC to see if the knocking subsides. Like I said, I never noticed this until I set the IP timimng to specs. It didn't do this at 15deg BTDC. It just smoked tremendously at initial start-up.

Kevin