Pissed off with motor, want to change
Anything that causes unburnt fuel in the exh can cause popping. So yeah, the carb could be the culprit.
I agree. Many others have suspected the ignition system for causing the exhaust pops. Sounds likely though I have never experienced it from ignition problems.
Re the carb, if overly rich, unburnt fuel can get to the exhaust. It usually ignites since most cylinders are still firing. An overly lean charge can cause misfire, which also puts unburnt fuel in the exhaust. This is often seen when decelerating with the throttle closed. I played with a Ninja 250R motorcycle carb recently. It has a "decel enrichment" valve (forgot exact name) which adds fuel during high vacuum decel to eliminate popping. If all cylinders are running lean and not burning, you probably need a hot exhaust to ignite the charge.
I have a Holley Projection TBI on my Newport. I think the injectors leak since if it sits ~30 min and I start it, I get an exhaust bang (I think, though could be an intake backfire). I can avoid by pressing the throttle wide open ("clear flood" mode) then turn on (so no pre-spray), then crank and pull the throttle up quick. The controller got in a bad mode once on the highway where the engine became real sluggish, then "boom" and blew the seam on my sheet-metal muffler. I imagine it went real rich. After crimping the muffer back, it did it again a week later, at exactly the same over-pass 4 miles from home. They were doing construction, so I wondered if a radio transmitter messed up my controller. I then installed a glass-pack muffler so it will blow back at any tailgaters if it recurs. BTW, does anyone know the correct way to install a glass-pack? I oriented so the small cupped openings face into the flow. Perhaps more drag, but seems like should be quieter that way. No arrow on the muffer, instructions on the box or website.