Yep that chunk of carbon did it BUT it will do it again as well. I got
REALLY sick of pulling the EGR on my 94 S-Blazer for the same problem.
Solved it by getting one of the EGR gaskets with a screen over the
pintle. Hasn't bothered since. Another thing you may want to do is give
that engine a top end cleanup with some GM top engine cleaner. That will
break up and blow out a lot of the carbon that causes the problem and
make the engine run cleaner as well.

Just hit the dealer for a can of the liquid cleaner (not the spray
version) and follow the directions. DO NOT USE IT INSIDE A BUILDING and
make sure that the exhaust is aimed away from anything you care about.
It will be throwing a LOT of carbon and crud out and that stuff will
stain anything it hits. Oh and when you first start it and run it to
clear out the cleaner make sure you select an area that is kind of open
and try to pick a day with a breeze. Your van will be creating a smoke
cloud like a tank on the battlefield and you don't want that hanging
around a long time!