85 westy/1.9L/automatic -- the engine drives great -- I was running
TDC timing, but moved it to 5 BTDC and it seems happy there while
driving.  I bypassed the DIS and set the idle to about 850rpm when
warm as per bentley.

However, still having trouble getting my idle to settle down --  if I
have the idle air bypass screw open enough so it doesn't die when
cold, then when warm it tends to race (up to the 1500rpm fuel
cutoff).    If i have the bypass screw closed so that it doesn't do
that, then sometimes it likes to stall out.

I'm 99% sure the throttle idle switch is working properly.

Oddly, this behavior seems worse at 5btdc than at 0.  (I say oddly
because it sounds like most other folks have a smoother idle with more
advanced timing).

The engine runs smooth and with good power, but idles like cr*p --
seems like it's missing and has a slow-fast-slow-fast pattern, even
when it's holding steady near 850rpm.

My theory:   One of my prior mechanics drilled the AFM's adjuster
screw and may have changed that setting, back when I had vacuum leaks
and dirty injectors and a questionable ECU.     So, now the engine
runs great, but idles poorly -- maybe the cause is this misadjustment?

I'm about to leave for a long trip -- any harm in playing with the AFM
adjuster screw to see if the idle will smooth out?

According to a prior post re: the function of the mystery screw:
> That screw is for adjusting the mixture at idle -- it regulates a
> small bypass that allows air to go through the AFM without being
> metered.  You turn it while monitoring the CO level at the test port
> ahead of the CAT.  Once the throttle opens its effect is
> swamped.