i read about it since the beginning and because you tried different timing positions, i dont think its timing-related. a couple of years ago, ihad a similar bog at part throttle and a bigger shooter didnt correct it. a high flow power valve did, and i suggest you try holley number 125-165. first confirm it is the primaries that are lean by disconnecting the vaccuum pot from the secondaries by removing the small clip at the end of the shaft.make sure the secondaries cannot open and go for a ride. if it still bogs or pings you know the problem lies in the primary circuit and you should try the hi-flow power valve. you could also try to momentarily plug the pcv hose with a pair of vise-grips, it should help too.