HP in Albany

Sounds familair. My 2007 ES350 has a bad smell probelm for almost a year. I went to the dealer three times and the problem is still there. I have replaced the airfilter and asked them to clean the air intack with heavy duty deodoring liquids and also folllow the dealer's suggestion to turn on A/C and auto at the sametime. I also went to other local garage to clean it twice. The mechanics at the local garage told me that it is the heater core problem. Don't know what to do next.