The sticker essentially warns that the teflon (or whatever) coating can be easily scratched off. A soft cloth and TB cleaner won't hurt it anymore than hot exhuast gas from the EGR ports will. As mentioned the coating is not that effective anyway or we wouldn't have the EGR buildup probems many have experienced and cleaned up. I've not seen any faster buildup of gunk or ill effects from gently cleaning the TB and upper intake ports with TB cleaner. (Over 40K miles since initial cleaning...)
