I bought a home a year ago that was built in 2003. I'm having issues with air quality on the second floor. It has a dual zone furnace/ac setup where the zones are 2nd floor for Zone 1, and basement and first floor for Zone 2. Whenever I am upstairs (zone 1), my sinuses and throat get irritated. It is not unbearable, but it is clearly noticeable. I do not see any mold issues, any sources of moisture, etc. When we bought the place, which had been vacated, the furnace was not igniting, so we fixed that. I have a feeling that the issue is related to the HVAC system in Zone1. My questions are these:

1) If there is an issue with the air quality as a result of the HVAC, whom should I contact for help?
2) What if anything can i do on my own to remedy this?
3) What else might some of you suggest to look for in case it is not related to the HVAC?