Popping sound in exhaust

Good deal! Now I gotta ask.... where on the carb/manifold was the vacuum advance hose connected? I gotta admit that I am scratching my head on why this changed if it was on the port for ported vacuum. (Maybe I am just tired after a long day....)
I dont know which port the OP had the vacuum advance connected to, but it should be connected to full manifold vacuum for performance tuning.
If it is bone stock I would follow the factory vacuum line schematic. Some were connected to ported vacuum for emissions alot depends on the advance itself.