I used some spray mag wheel cleaner for raw aluminum wheels. It made the aluminum look brand new but did stain the black plastic plenum. I had to respray the plenum. Engine now looks new. One thing I did wrong was do it at the quarter car was while engine was hot. I believe if you are careful to not get any on the plenum. Try it on a small area.
2000 300M Silver, HID's, RB1, Sirius Radio, 6 CD Changer, 2002 wood wheel, EVIC with PSI, Steering wheel radio controls, 2002 12 spoke chrome wheels, 2002 mirrors with tiltdown and auto dim, Mopar spoiler Most Clean at Kansas City 2006, Members choice at INDY 2007 and Most clean at Carlisle 2007 & 2008 Most Cruising Carlisle 06, 07 & 08. Most Clean at Indy 2009 Almost Clean at Carlisle 2009 & 2010