I have the HSM "straight" pipe (a no-muffler, bent piece of identical-diameter tubing, non-mandrel bent, with a chrome tip). It goes axle-back, and is not sold on the basis of performance gains but for a change in tone. Heck, it was only $100 so I bought it - a little bling for the ears.
I can verify no "real" performance gains from it - it seems to allow the turbo to spool a tad faster but that's seat-of-the-pants and not backed up by a watch or dyno. Sounds great (as a performance piece).
BUT... my point is: it's a straight pipe in place of the original Racing Beat muffler, and, while fairly significantly louder than stock, it's it's not really THAT obnoxiously loud from inside or out. It's "livable", if you don't mind bing heard (sounds like an old Healey, or MG, or perhaps a slightly-less-raucous version of that new fast turbo Neon, the Newt, or something
)
I've followed my wife in the family MPV GTI as she drove the MSP (HSM exhaust on), giving a good listen. The MSP with HSM is quieter than all but one Honda performance exhaust I've heard. Leads me to believe a mandrel-bent, no-muffler, diameter-equal-to-cats catback (in SS, natch) would be acceptable from a livability standpoint - and may give some performance gains. From the inside, I can still hear the stereo fine, but the exhaust never really fades into nothingness like the RB muffler does, but it does smooth out at higher revs and when coasting (natch).
That said, the Racing Beat muffler isn't all THAT restrictive, is it?
-L
