I don’t have time for much commentary, but in case you are wondering…
2001–2003 are his admitted steroid years. They are also the years in which he played in homer-friendly Rangers ballpark.
If you look hard enough, you’ll probably think you see something, but there doesn’t appear to be much here. Yes, his homers went up when the AL’s HR rate went down, but then take a look at 2007 and 2008. Also, he was also still experiencing aging improvements in a helpful environment.
UPDATE: More here.