Very cool to see the build going on! Looking forward to updates...

TCS - will reduce engine power and apply one or both brakes on the drive axle to control wheel slip to improve 1) stability, 2) steerability, and 3) acceleration. So you can see, you don't want it.

I've been instructed that a factory-style clutch pack diff is the best, but maybe that's another sort of religous debate... I'm using one 'cause that's what was cheapest!
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All the debates on diff's I've seen rank the quaife third behind the clutch pack then a locker/spool/welded. Tuning the clutch pack is an art in itself, break-away torque as well as ramp angles and more can be adjusted. Good luck on the Boxter. I'd love to see you do well with it.

James