How long had it been since you last cleaned the tips? I have similar tips on my A3, and usually have to use an APC with a lot of elbow grease to make a dent in the grime along with 0000 steel wool. Then I finish up with session of Optimum Metal Polish.
If you're getting this sort of result with just one step, I will definitely consider adding the mother's metal polish to my arsenal.
Great job!








