go over to
www.autopia-carcare.com
They have a wide selection of wheel cleaners that are Porsche safe.
Porsche products I suspect, are nothing more than rebranded products at higher prices. And not very good.
P21S wheel cleaner is very popular. I recommend Waxing your wheels(and calipers) each time you wash them. Claying them after each wash gets off most of the contaminants that a simple wash leaves stuck to the pain surface and returns the shine to full gloss. I use Meguairs NXT, the only product from that brand that I use. (nice brushes though). My favorite Tire dressing is 1Z Rubber and Vinyl. Leaves a deep no shine look.