Be happy the coondition is present often enough to diagnose and fix! It's those "every two weeks after driving 50 miles at 65" that can make you drink!
Before you install the carb, check the plug's condition. Install the carb and run it again. Be ready to look down the carb when it acts up (flooding?), and have the MM connected to the coil to see if the input changes. If the carb isn't flooding and the voltage doesn't crop, it's most likely going to be the coil or ECU or ECU ground.

Also be happy it isn't the expensive internal stuff!