I’ve had my ‘16 FiST over a year and have had a Quaife LSD in it since July. No question, anyone buying a stock FiST who wants to get the most out of their car should first add a diff (ok, and an rmm). Wait on the intercooler, the tunes, the big turbos, the coilovers - put a diff in it and get to know the car the way it should have come from the factory, able to use all its OE power coming out of corners. Add whatever else you want after, but start with a diff.