It's probably safe to assume that he started in 2011 in KC. Coming off of his horrid year in Atlanta, he probably felt that he needed to try something to help because KC was going to be his last guaranteed shot at the majors and if he sucked, he would be doomed to minor league deals.
He showed decent ability in 2006, 2007, and 2009
I'm not going to say that PEDs won't help, but I believe that the improvement from PEDs is far less than people think. Especially when it comes to hitting in baseball. There's also a lot of evidence that suggests that he improved his approach to the plate.