96 Cutlas Ciera obd code 1406??

Went to get car inspected-no eng lite on or serv eng lite. Garage puts on NYstate computer for insp throws P1406 code say erractic misfirig problem fails inspection. What could be the problem?

Must have been a pending code if no lite was on? This is not a misfire code, it is for a bad egr valve or plugged egr passages, there are other sources of this code also, needs to be diagnosed.