Trouble code problem

Hey i went to autozone and got them to run a check engine light scan on my car and it had 2 codes. 1- egr malfuntion, which i knew was the reason the CEL was on.
2- i forgot the exact code but it was a catalatic effencentcie threshold problem. The guy told me it just means its not running level but it could be caused by the new turbo and the ECU learneing the new specs. What yall think.