I will buy most of what you offer except for the retarded part. PING is pre ignition. It can be octane related of course. The higher the octane the slower the burn. So you have to retard timing to fight ping. On modern engines that have ping sensors that is exactly what the computer does when the ping sensor sends it a signal. It will retard the timing until the ping sensor shuts up. Of course it could be running too lean as well, but I suspect it is too much advance. And I am not talking vacuum. I am talking mechanical. Not sure if you know this but your engine has both. The vacuum advance is only available at idle and once you get into a higher vacuum cruise mode. The instant you open the throttle to any adequate level for acceleration you lose all vacuum advance. One reason you are supposed to disconnect your vacuum advance when timing a car.
