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Re: Ur-Quattro

  On the stumble problem with the IA computer mod at 13-14 PSI boost, if
  the stumble goes away when you disconnect the vacuum/boost sense line
  from the computer it could be one of two things I can think of. 1, the
  CPU is detecting a (possibly false) overboost condition and shutting down
  the fuel system prematurely, or 2, the timing is being backed offby the
  CPU too much relative to the boost level, causing the stumble. I think
  you might be able to rule out the fuel-system shutdown by hot-wiring the
  fool pump relay and re-testing, if the stumble is gone, you know it is
  protective shutdown causing the problem. If the problem is too much
  retard as a function of boost, you're gonnah have to call Ned at AI and
  seek some advice. I do know that is it possible to vary the amount of
  retard as a function of boost. I think this is one of the differences
  between Stage I and Stage II, Stage II has less retard as a function of
  boost Vs Stage I.

  WARNING: With the boost/vacuum sense line disconnected from the CPU you
  should have extreme levels of engine-threatening detonation under boost.
  The detonation should be so severe that you should readily be able to
  hear it. I would be most concerned about operating the engine under boost
  with that sense line disconnected!!!!!!!!  If this is not the case, then
  perhaps something else is wrong that is causing the timing to be
  retarded, eliminating the extreme detonation you should be experiencing
  and possibly causing the stumble as well.

  Give Ned a call,