Have any of you guys had this problem? The stock chinese GNT plug didn't have this problem, but the champion & ngk plugs both leak around the seal (ran like **** with the champion L86C, but it might have been a gapping problem). And yes, it's tightened all the way down. It doesn't feel like the fit is sloppy or anything. Do you think it is safe to use permatex on the threads of the plug to stop the blowby?