You don't want any metal shavings make their way into the VVT actuator. Let me repeat: Absolutely NO metal shavings. So apply grease onto the tap, and remove the tap several times to clean out any shavings. Also be careful not to tap too far into the hole. NPTs are tapered in order to seal well. Tap too far, and your fitting might not seal. I think I tapped some 8mm into the hole. Regularly check with your fitting so that it almost completely goes in, but still has a thread or two left.