90 Corvette Pinging Update

[The Thibodeaus]

Tonight I changed over to the stock chip.  At WOT, the stock chip pulls out
5 degrees of advance at 5000 RPM just like the Performance Resource (PR)
chip.  At highway cruise, the stock chip pulls out 1 degree of advance under
light acceleration, the PR chip pulls out 2 degrees.  At 20 mph where the PR
chip pulled out 15 degrees, the stock chip pulled out 3 degrees.  One
blatant difference was the PR chip was indicating 0 duty time for EGR and
the stock chip was showing 99.4% duty time.  I have spoken with PR and am
returning the chip along with printed sheets of data from the PR chip and
stock chip for this 20 mph case.  They are going to send me another chip as
well as examine the data in the mean time.  So now I am left with the fact
that both chips are retarding my advance on the highway under light
acceleration and at WOT.  Should I suppose this to be normal?  The service
manual indicates that the knock sensor is used to allow maximum performance
which could be interpreted as "they run the engine right on the edge of
detonation".  If so, a slight tip in of throttle may be too quick and the
knock sensor has to respond.  I have also read that the front Corvette Y
pipe has one pipe which crosses into the other internally where they meet
such that one side of the motor is more restricted than the other.  My
thoughts right now are that maybe this is leaning out one side of the motor
and since there is only one oxygen sensor it does not detect this,
especially if it is on the rich side.  Any comments on this or other ideas
what to look at are welcome.  I also appreciate the comments I received from
my original post.  Although I am using Sunoco Ultra 94 octane, I may switch
brands to see if this helps the situation.  Thanks for any input in advance.

Bob T