FWIW, I had installed the MRT POD filter on my car awhile back. I liked it a lot. The sounds were great, as without an aftermarket BOV, I had no other way to get those "rally" sounds. I bought the MRT unit because upon reading the "Training WRX" book (worth having, but get the new 2nd edition), one of the authors felt the pods sucked more air than a CAI, and thus if the inside/outside temps were not over a certain % difference, then the pod wins hands down.
Now as for performance, I noticed that the boost went a bit higher (on oem gauge), came on faster, and throttle was more responsive. BUT. This is good while you are moving! If you AutoX like I do, waiting in line for your run can kill you! At one of our last events, a practice with a lot of laps, the outside temps at California Speedway were in the 120's! Under the hood could cook a steak in almost 2 minutes. I lost a lot of power then. So this time, the inside/outside % was great. But on a cold, misty morning, that car was amazing (of course, colder and denser air).
I have now gone back to the stock airbox, and though I no longer get the "rally" sounds, I am still not loosing power. Just a wee bit response loss, but not that much. So, for my next step, I am thinking of doing the resonator mod. Could someone please explain it to me? I have heard some mention to just cut the bottom off, and seal the top tubes off to make the front scoop blow right to the airbox. Another cut the box off at an angle so as to still get some fenderwell air in. What I was thinking, upon looking at the resonator, has anyone just cut the front of the bottom "tank" off so as to make it into a scoop? Seeing as it is facing the airvents on the side of the front bumper, it could concievably help to partially ram air in. What do you think?