Tartine + Sourdough Taste

I just moved to the San Diego area and began making my bread starter from scratch (it's 3 weeks old now) from the Tartine cookbook. I just made the country loaf and it rose perfectly and looks just like the pictures.

My issue is that is doesn't taste anything like sourdough bread. In the book I believe the author mentioned to extend the bulk fermentation phase from 3-4 hours to an extended period of time to create more complex flavors. So I extended that fermentation phase to 7 hours, but it still lacked the Sourdough taste that I was looking for (I'm comparing the taste to Boudin bread in San Francisco).

Is there something I need to add or should I just keep feeding my starter and eventually it'll get there? From what I understand it has to do with the bacteria in the air or in my hands, so maybe I just need my friends in the Bay Area to ship me some C02.

Thanks!