4.11 diff gears create more torque because it makes the pinion gear spin 4.11 times to turn the crownwheel creating more force. Its just adjusting a gear set to get what you want out of your gear set up, Custom machined gears in manual transmissions do the exact same difference but it requires more money and effort, you wouldnt really adjust it unless you really wanted to doesnt matter if its got a turbo or N/A the difference is the same. you loose top end because your putting in bigger ratios which loose speed but carry more force
