Yes, and Q4 have Torsen rear diff, much better then Dedra's
This is right, but I heard from "unchecked site", that the more simple Dedra diff should hold more torque.
I cannot prove this, but years ago I read a thread about a really powerful Integrale doing quarter miles (about 800HP), its owner changed from Torsen to cheap Dedra diff after certain rear diff defects, because it should be stronger (maybe these diffs are cheaper, only - as I stated, I cannot prove this)
Up to now I do not have any problems with rear Torsen with really much power, but nevertheless this statement is very interesting.