I have done a few Roush supercharger kits on the 5.4's. The kits are extremely nice and come with very detailed instructions. There was not a single piece in the kit that had to be modified and the fitment was perfect.
You do not need to change injectors, actually the only thing that needed to be done was to have the PCM re-flashed (which is included in the kit, box and shipping included), and different spark plugs installed (also included). Otherwise the kits can easily be installed in a day.
The kits I have done were non-intercooled, and were advertised as a 100 hp gain.
Gotta love the sound too.
