I clean my powervalves on my RS every top end. You would be suprised how much carbon builds up on them so quickly.
I soak them in mineral spirits and then use a flat edge tool to scrape the carbon clean from the flapper valve. I then use some scotch brite to clean them up really good. making sure there is no carbon anywhere on the valve.
Generally the pocket in the exhaust port where the power valve sits doesnt get any build up in there so you don't need to worry that much about cleaning that up. But I do use scotch brite to clean up the entire exhaust port of any carbon build up.
if the power valve is jamming, or not closing all the way, this will put un-needed load on the servo, which will in turn overload the PGM and burn it out. So yes, your power valve operation and adjustment is very important.
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Charles Gallant