1. The whole under side shape of the tank above and around the air box has been altered, it may have effected airflow and tuning.
2. The tank mounts/supports have been altered, rear attachment point has been changed, this could be responsible for resonance/harmonics.
Only way to check now is to borrow a stock tank, tank rear mount and stock seat off another Bellagio.
Or put my bike back on the dyno to see if A/F ratio has been upset.