I finally looked up what I bought. It was from Bavarian Auto Sport.
They do not say what brand it is, but I called and they said is was
made by Bosal. It is the same as what they are currently offering.
The exhaust and install kit would cost about $275 and most of an
afternoon to install it. Maybe their quality has improved since May of
Posters to this thread have recommended Eberspacher exhaust. Can anyone
point me to dealers that sell this? Another alternative is Midas.
They do not say who makes it, but I believe they warrantee it for a
long time, and it would mean I would not need to do it myself! They
want $670 though. It is just a bunch of steel tubes, right?