i used the permatex copper spray gasket in a can for my o2 housing connection to the manifold, and i used it for a few weeks but the o2 housing joint was leaking so its off right now and im trying to clean the flanges so i can fix the leak but i can not, for the life of me get the baked on copper spray stuff off the flange. is there any way to remove the copper shit?? its almost as if its part of the metal now so i cant make the flanges flat and clean. i been scrapeing at it with a razor now for 2 hours and useing metal polish but i cant get it off. anyone have any clu whats the best way to remove the copper spray on the flanges. or shoould i just spray a new coat right over the old coat?