[olddog]

I have read some top notch efi tuners who say on performance cams you should adjust the idle afr with a vacuum gage. Find the afr that gives the highest vacuum. With efi it is a bit easier, because it will hold the idle at the same rpm. With carb you will have to watch the rpm and correct it. You have to keep the rpm and timing constant or you are letting multiple things that affect vacuum change at the same time.