<VV> non corvair engine detonation question - NO VAIR

[EVERETT WILSON]

My daughters granny mobile (1990 Caprice Classic) has a 305 v8 t.b.i. that has commenced to ping.  A Lot.  As soon as it goes closed loop, it pings and pings and pings.  Mostly at tip-in and any light throttle.  Goes away with brisk acceleration, but then its back.  Has thrown a code 32 on the trouble code list.  Thats EGR system.  I have removed the valve and cleaned it out.  Cleaned out the passages in the manifold.  Reinstalled valve with new gasket and operated it by hand at idle and the engine stalled, so I believe the passages are open.  It has a new water pump (it was noisy) and new thermostat.  Have run various cleaners thru the injectors.  put a can of SeaFoam thru the manifold to clean out carbon buildup.  New PCV valve.  Checked hoses for vacuum leaks.  Etc. Etc. Etc.
   
  I was given a new o2 sensor (its even the right one!!) so Ill put that on tonight and see what happens, but meanwhile, do any of you know how to test the EGR circuit to see if it is actually opening the valve?   Applying vacuum to the valve does nothing, but I have read where that is normal as it needs back pressure before it will work and I have been without an assistant to open the throttle while I manipulate hoses and observe things on the other side of the engine.
   
  Anyone out there had similar experience and found a fix?  The budget is shot, so I cannot be buying more parts if I dont need them.
   
  Everett Wilson
  North Richland Hills TX