Put the Stromung on the wagon today, along with a K&N filter, and I love it! There is a smidgen of low end loss that is barely noticeable, I think because of the 2.5" diameter. But it pulls like a fiend! The butt dyno says "Hayul yeah!"
Oh. And the sound. Well, put it like this. I heard this KILLER sounding car coming up and said "Hey, whose car is THAT?!" "Yours," said the guys at Duxler Tire. You could have used my grin as a light source.
It's most assuredly louder than the stock exhaust, but duh. It isn't intrusive, except at WOT, or at lower revs, both zones in which I spend little time. My wife doesn't think that it's bad at all, and I agree. And it sounds absolutely wonderful, the kind of deep growl that turns heads.
Another tidbit for the class. You can reduce the volume of the chamber that the Stromung resonates in for you wagon owners with two things: the rubber pad that Subaru sells for the cargo area (which I use for the muddy bike stuff anyhow), and by drawing that privacy shade that the wagon comes with.
Things seem less peaky, too, as if I'm getting more pull throughout more of the rev range, and I only set off one car alarm.
I also installed the KVR x-drilled rotors from the group buy with stock pads, stainless lines and SuperBlue. The difference is pretty wonderful. I'm sure that some of it is attributable to just having a new set of everything put on, but the braking performance is a hoot, based on my very mild use, as they brake (sorry, couldn't resist) in.
This KVR rotor thing will be an interesting experiment, re the cracking that people say occurs with x-drilled rotors. I had mine cryo'd, so we'll see. They look fantastic, peeking out from behind the wheels. Should look amazing with the P1s.
That's all for now, and sorry this is so long, but I wanted to assuage the concerns of those who might have been considering a Stromung for a wagon or Outback.