It might be another crappy Comp Cam problem.... seen a bunch of them lately... mainly lifters... when he started the post he was talking about "tapping".
When you have major ignition issues where its not firing at the right time it'll bleed the lifters down on the affected cylinders, Firing when not on compression stroke & the valve is still open. He was also talking about backfiring through the carb as well, If you read his later reply he mentioned the lifters settled down & it runs much better & not missing or backfiring after messing with the ignition..
I've also seen flat cam lobes do this too, popping back, But thats when the cam is really bad & has a few flat lobes, I'm sure he has checked to see if all the rockers where moving. He also clearly mentions in his original post about "backfiring" along with tapping lifter noise. Links below.
