well, its not really any certain rpm, its a certain throttle opening. Just an example, if its at 4000 rpm at 98% throttle opening, there is no ping, but open it that last 2% and it pings a little, even at that same rpm..The timing is all in at 3200 and it never pings unless that last tiny bit of throttle is opened, thats why i was thinking it was a lean condition. Heck, when halifax setup this distributor, he even dialed in the vacuum advance which is runs it up to like 50 degrees or something and it STILL doesnt ping when when the vacuum is working..Obviously the vacuum advance drops out when stabbing the throttle and i didnt even run the vacuum at first and it still does this, so it has nothing to do with the vacuum advance. Its just that last teeny bit of throttle..I know i can richen the secondary mixture some by limiting the secondary air door from opening so far in relation to the secondary butterfly opening but not sure if it will help. I think its propbaby the cylinder pressure like PRH said. sucks because some run more than 9.5:1 without this issue..just my luck