6% of one another, the Torsen will be fine.
ABS and ESP should also be ok within this tolerance.
However, a smaller spare tire may present a problem to the Torsen, and safety systems if driven very far at all.
Since the front tires wear faster than the rears, you won't be able to rotate them.
Also, the car will understeer even more than it presently does, so this is purely a cosmetic upgrade at the expense of handling. Quattro Audi race cars run wider wheels up front whenever allowed by sanctioning bodies.
The ideal solution if you want the look, is to run wheels with the same width but with different offsets to create the bumped out rwd look without the downsides. After all, wider rear wheels are first and foremost an attempt to harness power that might not otherwise get to the ground in a 2wd car, or to correct for handling flaws that might make a car tail happy. Neither are issues for streetbound Quattros :-)