My check engine light randomly came on. Called onstar and they said it threw 3 emissions code pertaining to the EGR valve. I have had the blocker plate on for the past 110,000 miles (no finger stick though) usually it throws 2 codes when onstar diagnoses it and the check engine is never on. They said code is telling them the EGR valve is stuck. The truck has been running like crap lately too. Kind of like the fuel filter is clogged but the filters only have 200 miles on them. Anyone have a clue???

I would check the mass airflow sensor. and definatly get a finger stick.
What number codes did it throw? I had one with the egr and it was my mass airflow sensor messing up. Try cleaning the maf sensor with some electrical contact cleaner if you have a cold air intake you could have got some oil on the maf sensor.