By DAVID B. CARUSO The Associated Press Tuesday, May 10, 2005; 6:30 AM PHILADELPHIA -- Philadelphia's former treasurer became the highest-ranking official convicted in a series of probes targeting what U.S. Attorney Patrick Meehan has called a "culture of corruption" in Philadelphia city government. Corey Kemp, 35, was convicted Monday on charges he accepted free trips, Super Bowl tickets, cash and other lavish gifts to help businessmen obtain city contracts. The corruption probe became public in 2003 when police discovered an FBI bug in Mayor John F. Street's office. Street has not been charged, and no evidence in the Kemp...