As for inlets, it seams it depends where you go.
Ive always had positive feedback from the ones I do, whilst others claim to see 0-2bhp. We are yet to have solid power figures for advertising, put preliminary tests show circa 8bhp peak with a gain of upto 10bhp midrange.
Ive said it many times before, "matched inlets" is used too generically and loosly. IF people are JUST simply matching the port joints, then im not suprised there are such little gains floating about. There is ALOT of work to do from the entrance to mid-way up the port, on both sides.
Gains in power come from gains in airflow, which is about reducing energy losses through transition in shape/profile, removing a lip in a joint plays a relatively small port in this (especially so in the RS3).