I am wondering if there is any data supporting that this mod actually increases anything other than noise. I did the Peaty version (everything outboard of the filter box removed, foam sealer between box and fender, plug in hole). It sounds cool when accelerating, but the humming sound is kind of annoying. Lustreking in the Legacy forum said his G-Tech time didn't improve at all with the mod.
I am thinking about undoing at least some of it to try to stop the humming. I might cut it so that the part coming down from the factory fender opening (which is now blocked) is gone, but all of the silencing chambers are still there. This would remove some of the convoluted factory tubing and still pull only fender air. Since this would be pulling air in from fairly high up in the fender, I think it would be fine to drill some 1/4-1/2" holes in the liner right behind the bumper since it would be very tough to suck in any water. What do you folks think?
P.S. My car in a '97 Outback which I think has an intake setup like the '98 RS...