have a listen

If you have a dial indicator set it on each rocker on set your dial at the highest point (zero) and then slowly hand turn the engine and record each cylinder. ( disconnect the battery)
That will see if you have worn out lobe... If all good then check your valve gap, timing. get a good timing light so you can set your gun to the timing you need.
You don't know the history of the engine you mitt have a burnt, bent valve, I've also seen the cam button come out of the cam and bend several valves.
Check these few things and if not good/ then I would pull the timing chain cover and check all details, chain, gears, loose cam bolt, ect. If that's OK then being that far into it I would pull the head to visual spec all.
Just a rule of thought,,,,,,,,,,,,popping in exhaust is timing,,,,, popping in carb is valves..............trying to help :D