08 EGC stock. Noticed lately my front cyclinder plug is darker than the rear. Also there is a ring of oil/gas (not sure) around the base of the plug resting on the outisde of the cylinder right where the plug threads in. I have noticed this plug seems to have more "give" than the rear. By that I mean when I am tightening it down, it doesn't come to a clear definite stop but seems to always have a little play. I am afriad the threads are leaking...will this damage valves or anything??