Quick update after driving for a few weeks: Super happy with the TMC. Also my mounting on the back of windshield fluid box (ended up using a glue gun plus duct tape in case it should break from vibration, plus stripping the wires) is smooth enough.
In my mind I feel I have a tad bit more turbo lag than I had before, but in any case (both from subjective feelings and repeated timings) the car is significantly faster. Also, the cold engine start sound is eeeeeven cooler than before!
Nerd-sidetrack: Curious how the N20 is assembled? Have a look: