Code 42 revisited

[Subfixer]

As discussed in an old thread, I get random detonation, followed by the SES light, secondaries are inhibited. Code 43 comes up as the problem. No other codes are set.

I had previously installed a new knock sensor which did not solve the problem. All checks in the FSM are good. Car is stock except for Mark's chip. Problem is present with or without Mark's chip.

While working on a radiator swap, I figured I would pull the plenum and have another look at this problem.

I found the secondary vacuum valve was leaking by, so I put in a good one, and installed a new vacuum check valve also.

I checked the ignition module for bent pins, but found none.

Any clue as to where I should check next before I button this up?
I do have a spare used Ignition module if I need it.

Thanks