Check the intake boots between the carbs and head. They have been known to crack right where the clamp is causing a lean condition. Need to look closely.
Unplugging the Throttle Position Sensor on the right carb has been know to eliminate popping on deceleration without causing any noticeable change in performance. I ran mine like that for years. Very hard to unplug though. Do not remove/unscrew the TPS from the carb!!
