Popping in exhaust

Definitely agree. Start with the simple checks first. I was a driveability specialist for 30 years and it's usually the littlest things wrong.
Check for vacuum leaks. Especially for any bad vacum hoses attached to the intake runners of cylinders exiting out of the left exhaust. Check the pcv valve. If you have power brakes check the booster for leakage. Also check the idle mixture screw settings. Simple visual checks may find the problem. If not any of these do a compression test. This will show up a burnt valve. Check how the plugs are burning. This could clue you in as to which cylinder is the problem. Champion makes a poster that shows you how various plugs look when there is a problem. Also make sure you have the right heat range plug in it. It's just my personal opinion but if you are running Bosch plugs throw them in the trash. Just have had too many bad experiences with them. If you can find a shop that still uses a scope it helps to find bad plug wires and you can see if the coil and plugs are firing correctly. Also look inside the distributor cap for tracking lines. Also this may sound crazy but if the dist. cap is gray plastic throw it out. They have an affinity to moisture and cause problems.
Basically popping is a lean burning problem with the gas mixture.
Good luck on your hunt!