Knocking Problem in 1990 Corvette L-98

[The Thibodeaus]

I have a 90 Vette with a ported plenum and Performance Resources chip with a
few other minor modifications.  I am having a problem with pinging and have
been monitoring the engine with an Auto X-Ray system.  The porting of the
plenum involved removing the walls behind the throttle plates but in front
of the EGR passages.  I think they may have been there to establish a low
pressure area for introduction of EGR.  With them removed, I may have upset
the pressure balance of the original design.  I have found my pinging
problem to occur in two block cells, number 10 and 14.  Does anyone know
what these cells are defined as?  Block 14 occurred
tonight at fairly low speed (28 mph) and 28% throttle angle.  I don't have
the data on block 10 but it occurred at around 55 mph with slight throttle.
My block learn numbers are also kind of low for these two cells.  The rest
of the cells that I have observed so far range from 120 to 132 so on average
I am in the vicinity of the magic 128 value.  Does anyone know if these
cells are controlled by programming in the chip.  I am suspicious that the
new Performance Resources chip I installed is the cause of this problem as
they advertise "modified partial throttle" enhancements.  Also, I do not get
any retard at WOT until about 4000 RPM after which the amount of retard
grows to about 5 degrees at 5000 RPM.  Is this normal or is this another
chip problem?

Bob T