Trying to remember the test...

Isn't there some way to open the EGR manually when it's idling? If you do that, it's supposed to stumble & maybe stall if the EGR is open & working at idle. (EGR is never supposed to open at idle.) I don't remember if you can push on something with your finger, or if you have to use a jumper wire to energize the solenoid or something...

 

Test usually uses a hand vacuum pump to pull the EGR open. It should stumble due to excess leaning. You can branch a straight vacuum source from intake manifold direct to EGR vacuum nipple and do the same test.

It is possible to manually depress the EGR open by pushing on the diaphragm in the cutouts of the EGR valve body. I've done this but worrried I might damage the diaphragm.

If engine does not stumble when EGR is forced open, then EG flow is blocked or EGR valve is not opening, if vacuum is applied. Cleaning EGR ports and confirming EGR valve function is fix.

If engine does stumble then EG is getting into intake manifold and may be OK. It's still possible for EG to be forced into perhaps only one port due to blockage of other ports. This result would suggest that something other than excess EGR is causing pinging.

good luck