I'm second owner and the original owners had this vehicle service almost exclusively by a GM dealership. I figured the cabin air filter had to be changed routinely as everything else was. I notice I'm not getting enough air out of the vents. I check the cabin filter area and it is loaded with leaves and twigs. I remove that and find the top of one of the filters covered in a sheet of dirt and debris. Next filter is covered with debris also. The amount of stuff that came out I wondered how I had any air getting through. I clean it all out and place back and air is flowing great. Don't assume anything!