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Yes take a look at the cabin air filter behind the glove box. it pops out easily and is most likely dirty and restricted. Clean it off if it is a screen style or just remove it and see if the airflow is improved and replace as needed.
Ok does the blower motor blow at full speed. You mentioned replacing a relay. If there is no air restriction through the cabin air filter, I would suspect a weak blower motor itself. With it removed it should move fast and push a lot of air, if not, I would suspect a weak blower motor
Then if the blower motor is working properly one of the interior blend doors inside the heater/ac box behind the dash is not working properly, restricting the air flow. A diagnostic test for codes of the HVAC module(ac control module) might show a code to point you in the proper direction.
Only if its a temperature blend door, there are several mode doors inside the heater ac box to direct airflow
Post your vin number and ill see if i can find any more information on your concern
No problem. i can check a few other things once I have the VIN
Ok there is a Technical service bulletin for reduced airflow but after extended driving and it calls for reprogramming the hvac climate control module. This may be part of your concern, since an update for themodule is available I would start there or at least run a diagnostic on the hvac module which would have to be done at a dealer unfortunatley