I love my OZ SLs but it used to take longer to clean them than my car. I just used DuPont Teflon wheel cleaner on them. Awesome.
Just spray it on, count to 30 and hose it off. I just got my 1 hour wheel cleaning job down to 2 minutes!
Got the stuff at Pep Boys, worth its worth in gold. I am going to try it on the other cars now, this is almost fun.

The paint came off my previous set of boxster calipers.

<img src="http://pictureposter.audiworld.com/22663/dsc04325.jpg">

It's a spray on gel cleaner that contains no acids, lye etc. I bought it to use on the BBS wheels on the Miata and it works like a champ!