The stock class says to have an oem differential but can i switch it to a different final drive ratio or do i have to use the one that came on my car? the new one would still be oem? Also are their...

could i also switch to the am session? if space is still available?

Does anyone have an RTAB tool i could borrow? i could pay for shipping both ways or i can pick it up and return it? I will also be at the Autocross next weekend.

Thank you,
James