I’m surprised that I have the work truck air box, because I have the Nevada edition which is supposed to be a trim above work truck (equivalent to sl) I ...

I’m surprised that I have the work truck air box, because I have the Nevada edition which is supposed to be a trim above work truck (equivalent to sl) I believe. Attached is a pic of my RPO codes. Has anyone modded this type of air box to take a filter without the kit? If I cut where shown in previous pictures what will I find? It looks like a spot where a filter could be added.... sorry for the slow response, I have been slammed and thanks for all of your help!!!

GM says cabin air filters cannot be retrofitted into trucks with RPO C67 in their TSB.
Judging from the RPO list on your SPID you are indeed SOL on this.
The tech service bulletin number is PI1216
https://static.nhtsa.gov/odi/tsbs/2014/ ... 0-9999.pdf