I have used extractor systems on both my '68 Bug and '70 Bus.  I had no 
problems
running them on the Bug but only got about 2 yrs. life out of the ones I
ran on the Bus.  I have used Thunderbird on both cars and an S&S on the Bug
and a Phoenix on the Bus.  Only slight HP gain(obviously more noticeable on 
the
(Bug) and though the increased sound level was not unpleasant or too loud, 
was significant compared to stock(have to turn the radio up to 11 instead of 
10) :).  I went back to the stock system on the Bus.  Genuine muffler from 
Germany(Ernst I believe, neat little decal for Formula Junior racers on it 
when I got it).  Seeing how it has lasted longer than the previous two 
exhausts under the same driving and similar weather conditions I can't, 
complain about the higher(about $50) cost.

Charles Armstrong
carmstro@ssf3.jsc.nasa.gov

'70 Bus