Hello I will help you with your question,
You do not have a cabin air filter on this year.
here is the statement from the service information
This Article has been updated by bulletin #PIT3330, dated December 22, 2004.Condition/Concern:A customer may inquire about the availability of the passenger compartment air filter.Recommendation/Instructions:Starting in 2003 model year, the passenger compartment air filter is no longer available as a factory option. With the redesigned HVAC case, there is no longer a cavity for the filter. The GM parts catalog indicates there is a replacement filter available; however, there is no provision for it.
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so that I understand completely. my suburban comes from the factory with no cabin filter
You are correct it was not an option to install one for this year as there is no place for it to fit in the HVAC case
Let me know if you have further questions about this