I am having heater air flow problems in the cabin.

This is a likely cause for the issue, if the cabin air filter was missing. You might try sealing off all the outlets except the one most likely to be in line with the heater core, removing the cabin air filter and placing the hose from a shop-vac in the filter cavity( duct tape is your buddy for doing the aforementioned steps) Making sure all controls are set to the max heat position, apply compressed air to the remaining duct, if there is garbage in there, this should mdislodge it and be captured by the vac setup. Let me know if you have success with this. If not, I can find the easiest access for you to physically see if it is indeed your issue. Hope this helps. DocDTC