well my guess is that the over flow of water that can't get out the drain leaks into a support in the unibody structure of the roof. I would also guess that this particular support is connected to where your reading light switches are and that they are lower than the drain. So the overflow is just following gravity and ends up in your switches (which are not totally water tight).
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.