By BETH HARRIS Michael Phelps led all the way in winning the 200-meter butterfly at the Pan Pacific championships on Wednesday night to extend his eight-year dominance in the event.The American touched in 1 minute, 54.11 seconds, fastest in the world this year. He finished a body-length ahead of Aussie Nick D'Arcy, who was timed in 1:54.73 after coming into the final with the world's fastest time.Takeshi Matsuda of Japan was third and China's Peng Wu fourth."The last 50 hurt," said Phelps, still breathing hard minutes after the race.