The filter noise should work, yes... but you have to run it on the mask.. make sure it's selected and run it... but now that I'm thinking about it... it may not work like its supposed to...no I don't think it will work like that.. i'd have to check it out...

do you have the PSD for it? I could try some things to see what works...

I think I've seen that type of parchment before... and if memory serves your best bet is to get in there with a fine brush and just mask those stray pixels out of there... believe me.. I know what a pain that is