I don't want to sidetrack Matt's classified too much, but I just want to say that using a little care in it's use, I have had great results using acid. It won't hurt the plating, so as long as you are careful not to let it run down into a port or up to the chamber where it will eat the aluminum cylinder material, it really does work quite well at removing transfer. Now I haven't done 100 cylinders that way, but I've done a handful and have been 100% successful thus far. I don't know how acid would make those spots in the plating.