Which of the extractor exhaust systems are the most sturdy?  I've been
told that there are two manufacturers: S&S and Thunderbird.
If so, which of these is marketed by BugPack, Empi, Rocky Mtn Mtrwrks,
etc.? I think I'm interested in a dual quiet pack for an early bus (Type
II engine).
 
thanks,
        Mark
        mthomas@tamu.edu