After tearing off the heads to have them freshened up, I noticed numbers stamped on the pistons. I was told by the previous and original owner that the motor was balanced and dyno'd. It does have all the dyno hook-ups on it so i never doubted him. He told me not to touch anything, just keep up the maintenance. Someone told me the numbers were how many grams were ground off that piston so they would be the same weight. Is this true ?