Originally Posted by bearsfaninwisc
again usually a missfire will set a code and the gm mechanic would have been able to see a code for a missfire!!!!
I think you are on the right track seeing as a vacume leak can cause a egr code to pop up!
I think we've covered the misfire already. My statement was preventative, not causal. I don't think he'* getting any symptoms from the plugs...yet. But he did mention that he changed 2 cracked plugs that cracked during installation using a bad socket. Usually, more than just two will be cracked in this case, and can start to cause issues fairly soon.