Bundy man- I've noticed that with the OS plugs as well on some motors, but not on others. I think it's more the particular motor than all TZ's. However, I know how to fix the problem- You're most likely noticing the leakage after installing a new plug when the motor is cold. Since turbo plugs are taper seal, when the button gets hot the aluminum expands slightly making the plug not as tight as when it was hot. Just take your plug wrench and snug it a bit when the motor is hot. For future reference, if you ever try to take the plug out when the motor is cold and it seems to be too tight, just start the motor and warm it up a little or use your heat gun to warm the head and it will come right out.