Paul, I do not know the answer to your question, but I offer these thoughts for you to consider.

1. Are these engines balanced internally or externally? If external then a change of the front pulleys may be required that match the turbo flywheel?

2. In theory, changing the flywheel weight could change the torque range and this may change fueling requirements of the IP in that range.

3. There maybe a relationship between a lighter flywheel and turbo response??

Was it NCDiesel that just had a engine balanced? If so maybe he can contact the person that balanced his engine for some more information.

crossbones