My '94 S10 has always had this issue almost annually. Every late summer into early fall I find one day after a long drive my idle surging and the engine running rough. I know right away to remove the EGR and clean the chunk of carbon that has become lodged in the selenoid plunger.
Early on this was considered a recall I believe, or at least was covered under a service bulletin.
Was there anything else I can do to try and prevent this from happening?
Well, besides installing a blank plate under the gasket..........
I just resigned myself to expect it at some point each year and it has always been old faithful.

 

Carbon chunks flake off the passage between the exhaust manifold and the EGR valve. Cleaning the passage will dramatically reduce the likelihood of having another chunk stick in the valve.

You also may be able to get a screened gasket that would not allow chunks into the valve.

 

My 95 used to do the same thing. Tried carb cleaner, tried carb cleaner and long brush (to scrub out the passage up to the egr valve), tried the GM upper cleaning foam in the can. Gave up and blocked it off with a small piece of pepsi can. My brother in law had a 96 that did the same thing. He got tired of taking it to the Chevrolet garage and just sold it and bought his wife a Hyundai.

On the other hand my 96 has never had the problem even once. Same gas, same driving conditions.

 

swartlkk what would you use to clean out the tube from the manifold to the egr, and were would i get a brush to clean out the tube with out removeing it from the blazer? i have tryed the carb cleaner and new egr but still code 401.someone told me if the egr was off and i started the motor it would run fast but mine almost dies. till a cap off the maniflod side. I thank you for any help.