Oosthuizen's second 66 nets Houston lead HUMBLE, Texas, March 31 (UPI) -- Louis Oosthuizen fired a second straight 6-under-par 66 Saturday, establishing a two-stroke advantage after three rounds of the Houston Open. Oosthuizen, the 2010 British Open winner, missed the 54-hole tournament record by a single stroke en route to the lead, and was especially tough on the back nine, where he recorded four birdies over five holes. The South African is seeking his second career PGA Tour victory -- he has four titles on the European Tour. Grabbing second place at minus-15 was Hunter Mahan, who carded a 7-under 65 on the Tournament Course at Redstone Golf Club. Second round co-leader Brian Davis slipped to third after posted a 3-under 69. There he joined Carl Pettersson (67) at 14-under 202. James Driscoll (71) finished Saturday two strokes back at minus-12, while defending champion Phil Mickelson carded a 2-under 70 to share sixth place with Ryan Palmer (66) and Keegan Bradley (69) at 11-under 205.