Your earlier post stated your timing is 15* initial plus you have constant vacuum hooked to the vac advance giving you 30* at idle. That is too much timing and is probably the cause of your popping at idle, not a lean mixture. Remove the vac source and plug it so your back to 15* initial and see if your idle popping stops. 20* timing at idle is max for any small block and a mild cam like yours is more like 15*.