Okay, so you know you’re on the wagon when you’re considering swapping out your 3.73 Limited-slip differential ( 3k RPM @ 70 mph ) for a 2.93 diff from a 325e. If my autocross days are over, then switching-over to a diff less mechanical advantage would cause immediate gains in fuel economy.
*** nerd factor 4 time ***
Using the calculator found Here
gear
rpm
3.73 (stock)
3025
3.25
2636
2.93
2376.965