I've read both posts so I do infact know what you replaced and tested.
That said, here is some info on your EGR system you won't find in any
book.

Toyota's early 4 cyl. OBDII EGR detection often incorrectly labeled an
excessive EGR flow condition as "P0401 EGR flow insufficient".  The
typical cause of excessive flow was a failed VSV (blue plastic VSV with
two hose fittings under the intake manifold) -- even though the typical
code set was P0401.

Did you replace the VSV with a new one?  EGR VSVs test good most of the
time.  What happens is the VSV will intermittantly fail on the road,
then start working again, making testing difficult.

The best thing to do is to Tee a vacuum gauge into the vac hose to the
EGR valve.  With a warm running engine, snap accelerate the engine to
2k - 3k RPMs and hold it there.  You should see the gauge jump off of
zero and hold somewhere around 5" - 10" (rough guess based on throttle
angle).  Then the needle should drop immediately to zero by itself as
you are maintaining RPMs.  This drop indicates the ECM is controlling
EGR venting properly via the VSV.  The fact that there is controlled
vacuum present initially indicates that your vacuum circuits and
modulator work properly.

Finally, hook a hose up to the EGR valve and apply full vacuum at idle.
The engine should die or atleast almost die.  A common cause of P0401
especially on the newer Toyotas (*actual* insufficient flow) is a
carbon buildup between the valve and intake port/mounting boss.

You mentioned something about an O2 sensor.  This system uses the MAP
sensor for EGR diagnostics, probably exclusvely.

Toyota MDT in MO