V8 surge problems

[Majewskier@aol.com]

I want to run this problem by all of you cyber trouble shooters.
 Unfortunately, as is often the case, I seem to have better luck at the
dealer if I already know what the problem might be, especially if they can't
diagose it via a fault readout...

My '90 V8 "surges",  for lack of a more exact term.  At part throttle. ie.
when cruising at a steady highway speed, I can definitely notice a somewhat
cyclic increase/decrease  in engine output. These cycles are about a second
long...+-+-+-+-+-.   The effect is subtle enough that it doesn't show up on
the tach or speedo, but wife and I have noticed it by seat of the pants.  It
is like the feeling of driving into intermittent headwind gusts (I have
eliminated that cause).  It is really quite disturbing..The car does seem to
develop good power under full throttle operation, but even under moderate
acceleration I can feel the symptoms. It seems to be getting increasingly
noticeable. 

Since writing the above, I am wondering if I am experiencing a bad Ox sensor
and if I am noticing the lambda? rich/lean feedback loop?  The car only has
thirty some thousand miles, but it is over five years old. It has had all
dealer related service performed before I purchased it, including the 30K
tune.  Could that expensive little Bosch piece be failing already?  

Also, I am also paranoid about the Seattle-area (m)ethanol gas from Nov to
Feb.  Especially because of this, I plan on changing the fuel filter soon,
since is not part of any dealer service, but I think these two things are
coincidental.

I would welcome ideas/suggestions.  Happy New Year!

Andy Majewski
'91 200 Q
'90 V8