I never bothered turning the t/c off on mine, only when booting it off the line when it was wet as the t/c used to cut in massively and cut off all the power rather than being progressive.

Induction kits do not work very well on the focus as they suffer with massive heat soak. The best power gains are to be had with a standard air box and a k&n panel filter, remove the resonator if you want some noise