wow meldy...your expectations for salespeople are so incredibly low that I'm sure you can never be disappointed in them. While I'm all for managing expectations, you should be aware that not all salespeople are simply pushers of products. Most of the ones in my industry (medical sales/device sales) go beyond merely being competent regarding the technical aspects of our products and how they fit into the needs/desires of the end consumer...and fall solidly into the expert level of knowledge. There are many levels of salespeople out there...both in knowledge and ethics. Although I have to admit that I have been blown away by most of the manufacturer's reps in the building industry...their lack of follow-up and technical knowledge about their products would not be tolerated ror long in my industry.

Were previous owners smokers? We redid a rental house & got new screens, 2 coats paint on each room, completely redid the kitchen, new cabinets, countertops, new appliances, light fixtures, etc. New floors & new carpet throughout. As we worked of course it was fall & had windows open. Right after realtor started showing the house to renters it got cold & we had to turn on heat, wow, did the house stink, we opened up that furnace door & it was dark dingy yellowed smoke, stale stink. so hours more of bleach water & cleaners before the place was pretty good. We added bowls of vinegar at night & hid them in the morning. by the time renters moved in it was pretty good. So try vinegar bowls where kids & critters can't get at them Open box of soda in closed in areas might help. Take a vent cover off & wipe out area of vent & rinse rag out in clean bowl of water, is it all brownish? Then it's probably the vents, if it is just dirty water with no smell that might not be it. I took a long skinny broom to couple of my vents a few times, got almost nothing out but I had gotten a high quality duck tape for attics & seams & so I guess nothing get in them to speak of. I have allergies big time, also clean out the area under furnace where air goes into to it from hall. I put a heavy piece of carpet pad that is covered with plastic on the floor under there & then wipe out couple of times a year by taking vent cover off. Of course no 1 smokes in my house but that area does get some dust. Yes fridge, freezers & humidifiers have drip pans that need cleaning or they can make you sick. Also if you have any drains that don't have water in the elbow sewer gas can come up & make you very sick, is there drain in center of basement floor- be sure to put gallon of water down it often or keep it covered, upstairs bathroom not used, get water in all the drains including tub or shower. Good Luck, Hope you find the problem soon.

Another option might be to under cut the bedroom door to allow the return air to flow freely where it needs to go. If your flooring or carpet is tight to the bottom of door, remove some of the door at the bottom. This move would be the most economical.

I just replaced an AC unit in a master suite addition. The inside part of the unit was very poorly placed so the choice was to remove it and replace or to go with a ductless mini split system. I picked the mini split. There is a head unit on the wall in the bedroom and another one on the wall in the bathroom. Unless the fan is on high speed I cannot hear anything coming from these units. Oops! Take that back. The unit we got has a condensate pump integral to the system. The only way to service that pump and reservoir was to remove the head unit from the wall. We decided to install a separate condensate pump that sits below the head unit. That pump goes off every 30 minutes or so depending on the humidity being removed from the air. In addition to the inside unit being very quiet, the outside unit is unbelievably quiet. The guts are outside. Then pipes go through the walls to the head unit where the cold stuff circulates through. The SEER is ridiculous at about 22. Here's a link to a picture of a unit close to what we got.