And the answer is...

[Steve Sherman <steves@cyrix.com>]

A while back I had asked the list if anyone knew the likely cause of my
rpm's overshooting the idle point on decel (eggoing to low) only to
recover a sec or two later...

I did not get any replies, but I think that I have found the answer...
both my 5KTW's were doing this, one quite severely the other not so bad.

The answer was the CO setting for the idle mixture.  It was set way
lean.  So that when one took one's foot off the gas, the rpms's would go
down below the idle point until the O2 sensor corrected things and
enriched the mixture a bit.  This explains the delay in coming back up
to idle rpm.  On the one car (which was suffering from some other
problems) the dip in rpm was occasssionly so severe that it would cause
the engine to die...  Adjusting the CO/Idle mix has cured this on both
cars.

I pass this tidbit on to others in case you see this problem.

HTH

Steve