I suspect this is because some are interested in using the data to try to determine the causes and contributing factors in the amazing rise on autism over the past 25 years.
Others who are likely contributing to the increase are interested in covering their butts.
I work with and supervise a number of teens or young adults with high level autism or aspergers. I empathize with your desire for more information.
This site has results from large surveys of parents about treatment success.
Autism Research Institute treatment parent ratings 2009 http://www.autism.com/index.php/treatment_ratings_asd
"Detox. (chelation)" 74% report "got better", 3% report "got worse", 23% report "no effect"
The 74% rating is the best of the many dozens of listed interventions.
GFCF and another diet were also highly rated.
I have links to more information on that if you are interested.
Since surveyed parents who have used heavy metal detox (chelation) tend to report encouraging improvements, I suggest that you look into that as a part of your attempt to improve health.
Remember if your insurance co does not pay for detox--most likely doesn't--don't expect your doctor do want to do anything about it. there are other factors discouraging doctors from messing with detox.
If you'd like to learn more about detox/chelation you could check out the chelation groups here and at Yahoo groups. There are a number of young people with high level autism or aspergers in teh groups.