The holes looked black but not blocked. I didn't probe down onto the holes though.
Part 1 -How to Test the GM EGR Valve (P0401, P0403, P0404, P0405, P1404, P1406).
Thanks cdminter59. This is the kind of info I need.
I will run through these tests. Looks like this should diagnose the problem. I do have a code reader, so that should help.