Is this a new problem or has the motor always done this? Did it ever "work fine" before?

You might want to take a look down the throat of the carb and see if your squirter is working. Maybe wire shut the secondaries with a bread tie and see if the "pop" goes away?

70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"