[FWB]

exhaust popping could be as simple as a header flange leak, or a lean condition from WOT.
while i do not condone using single plane intakes on the street, this could be the reason all is good at 3000 rpm and up, this is where the intake is designed to work. the pop could be the edel carb not keeping up with fuel needs.

the duraspark distrib. is a good unit, honestly i prefer them over MSD.
look for black soot marks around the header flange. pull plugs and see how they are burning that willl lead you in the right direction.

fred