I think I've diagnosed my EGR problem...am I right?

1995 T100 3.4/Auto Trans 327,000 miles

I posted here a couple of weeks ago about a P0401 code (insufficient
EGR flow) that is causing a CEL on my truck. I pulled the egr and it
looked clean and functioned normally with vacuum applied to the top
port.
I know that two other components affect EGR function - the VSV for EGR
and the EGR vacuum modulator. I pulled the VSV last friday and examined
it. It appears to be funtioning normally when 12V is applied to the
terminals - a definite click.
Next was the modulator. As I understand it, the modulator contains a
diaphragm that is connected via the larger bottom hose to the EGR
valve. Being a diaphragm, should it pass both vaccum and pressure
through the bottom port? Mine does. Both vacuum and pressure are passed
through the modulator when testing out of the engine. Bad modulator?
I know that the VSV has a much greater propensity for failure in this
motor, but when my local dealer quoted me $179.00 for a new one, I
balked just a little. The modulator is only $59.00.
Am I on the right track here?
All vacuum hoses are tight by the way.
Thanks all.