Pop pop on exhaust side

I think you first need to find out why idle vacuum is so low...& lower than expected for that cam. The low vac is why the idle timing needs to be so high. Idle vac is an indicator of engine efficiency at low rpms.
There can be many causes of low idle vac: faulty cam grind, cam lobes/lifters worn, cam installed in a retarded position, very low compression, valves leaking, air leaks etc.