This article is from the VW Performance FAQ, by with numerous contributions by Jan Vandenbrande others.
A:See the archives on Performance improvements as well as
the Wired article. The two most trusted companies for VWs
chip makers are Neuspeed and AutoThority. There are some
disputes that one is better than the other, but it's
mostly a matter of compromises. In regards to SuperChips,
their reputation has been tainted by some questionable
claims and 300$ improvements that had nothing to do with
reprogramming the chip (you get back the stock chip!).
AMS is also trying to enter this market, but so far there
is insufficient data on this.
 
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