There are pro detailer level wheel cleaners that are not sold to the general public in auto stores...too strong, you have to order them online from the detailing websites. If soaking in a safe cleaner like P21S wheel cleaner won't budge then I don't think pressure washing is going to fair any better. Seems like there's been some bonding.
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GT3 Recaro Seats - Boxster Red
GT3 Aero / Carrera 18" 5 spoke / Potenza RE-11
Fabspeed Headers & Noise Maker
BORN: March 2000 - FINLAND
IMS#1 REPLACED: April 2010 - NEW JERSEY -- LNE DUAL ROW
remove wheels and use oven cleaner not the cheep stuff let it sit for 10 to 15 mins scub with stiff brush and rince with lots of clean water dont get on you stings like hell