It started calling itself "Young Country" in either late '96 or early '97. I don't remember much about the lineup, but I remember Lisa Dent was the morning host.
To answer your other question, it was never as successful as Young Country in Dallas. It didn't sign on until the Young Country approach was on the downhill side. Really, KYNG 105.3 was about the only successful Young Country station of the Alliance/Infinity/CBS group. Seattle and Houston piggybacked on their more successful country sisters while San Francisco limped along for several years without gaining traction despite its more successful competitor going away due to an ownership change.