[Shotimes] (OT) clogged EGR tube or bad valve or bad sensor?

[van Oss]

Sorry for the OT post.

My wife's 94 Crown Vic (4.6L SOHC) has EEC-IV like a SHO.  Check-engine
light is on continuously after a couple of minutes driving, no matter the
conditions.  KOEO yields code 332.  According to the manual with the code
reader, 332 = "Insuffiecient EGR Flow Detected."  That sounds like clogged
EGR tube.  According to SHOtimes.com, 332 = "EGR valve opening not
detected."  That sounds like a vacuum problem or a bad EGR valve.

The EGR on a 94 DV apparently the DPFE (differential pressure feedback)
type.  The EGR valve/tube looks hard to access, the DPFE sensor rather easy.
Torry says DPFE sensor is $70.  I don't want to blow $70 on ruling out the
sensor, and I'd rather not hassle with the EGR tube if it's the sensor.

Can anyone tell me odds on this?  Any advice on tests, or what to try first?
Thanks.

Joseph van Oss