how to clean the air intake

Just wanted to add that when you spray your disinfectants into the outside cowl area, you nee to have the hvac system set to "fresh air" not recirculate so the disinfectants actually reach the evaporator coils, the heat cold selector moves a hot water valve not a temp door so the temp setting doesn't matter. If the buildup is bad then it may take a decent amount of disinfectant, and after applying you should shut the whole system off so it can sit and kill the bad guys. Good luck!

When you say you replaced the air filter, do you mean the Air Conditioning air filter in the dash? This filter can become musty if it is aged and dirty. This is a good place to clean as well. Otherwise...you are experiencing odor from your evaporator box...or plenum. This is where the condensation comes off of your evaporator core, and hopefullly drips onto the ground. In some cases, this drain hole can become plugged, causing moisture to become stagnant and start having an odor. If you continue to have no success, many good repair shops have a procedure that can perform to spray a special cleaner/deodorizer in the affected area for probably around $100 or so.

The 1997 Camry doesn't have a cabin air filter behind the dash but Dave is right about the odor. Clear away any leaves and debris from around the wiper blade/ front cowl area (that is where air is drawn in from). Make sure it is not water leaking into the car from a bad w/screen seal, door seal, or blocked sun roof drain that is causing the odor. Try spraying an aerosol anti bacterial disinfectant in to the air vents in the dash, let it sit awhile then start the fan (key on and spray the disinfectant into the air vent intake at the wiper panel are.