You mostly notice pin knocking at lower rpms when you have a load on the motor....Porcelain color can vary just by changing the needle position so I never use that to determine the main jets....Try this....run it for awhile to get some color on them, like old plugs, than run it wide open in 6th gear for 5-10 seconds, shut it down, coast to a stop, pull the plugs..Get the strap at the end of the plug to a chocalate brown color. If your worried about detonation, then look at the outside of the ring for any aluminum speckles...This will be pieces of the piston...