A low bake temp powder is required for a forged wheel. I have had numerous wheels powder coated with good results, you just need to know what your talking about when you inform the coater about the specifics of your wheels.
Cooking a forged wheel alters its state just like any metal. Keeping that temp lower will reduce the negative effect of basically oven curing your wheels.
With cast wheels I haven't worried about it and haven't had any issues. With a forged wheel however I am more cautious.