Induction pipe would mean from the afm/filter to the turbo
I'm pretty sure Apexi make one
but yeah, it would be easier to get an exhaust shop or fabrication place to make you one
17s will be more comfortable to drive on because of the larger tyre profile
18s will be bumpier, and you will feel the road more
not really sure what you mean by driveability
im pretty sure that
17s have better traction because of the larger tyre profile so more sidewall flex
18s would have better handling because of the smaller tyre profile and less sidewall flex
feel free to correct me if im wrong
in my car, thats a sensor to switch the thermo fan to the higher speed
but you have a clutch fan, so im not really sure
someone with an r33 should be able to help you