Oxygen sensor and high speed stumble UPDATE

[The Thibodeaus]

At 06:54 PM 10/29/98 -0500, you wrote:
>I have an 90 Vette with a L-98 which above 4000 RPM loses performance and
>it has been suggested it is starving for fuel.  The fuel filter has 500
>miles on it.  I pumped some fuel out of the tank tonight after shaking the
>car to check for any sediment and the fuel looks fine.  I am running an
>adjustable fuel pressure regulator set at 48 psi.  I pulled the oxygen
>sensor tonight and it had some black soot on it indicating a rich
>condition.  Here is my question, by upping the fuel rail pressure to 48 psi
>am I starving the engine at high RPM because the pump can't flow enough
>fuel at that pressure?  Does this seem logical?  I increased the pressure
>compensate for a ported plenum and also to overcome a pinging problem
>(several prior posts made to this board and Vettenet on this nightmare) but
>it hasn't worked.  I am working with the chip programmer to resolve some of
>the pinging problems because I have found that they completely shut of the
>EGR function.  So, should I lower my pressure?  Any suggested value?
>Thanks for any suggestions.
>
>Bob T
>
Today I ran the car up in second gear with a fuel pressure gage taped to
the winsheild.  The pressure never really dropped below 40 psi so it looks
as though the fuel pump is OK.  The knock sensor pulled out about 4 degrees
of advance maximum.  The oxygen sensor was reading about the mid 900 level
millivolts at WOT.  The maximum advance at WOT was 29 degrees.  One thing I
did notice though was that the Auto X-Ray never indicated open loop at WOT
even though my integrator and block learn were at exactly 128 which
indicates that it was not using these parameters.  Any comments are
welcome.  I don't have a correlation of oxygen sensor voltage to AF ratio,
am I too rich?

Thanks

Bob T