I can't figure why there is such a fuss about these heads. I drive my car to have fun, and have had no issues with the heads. My car was built in April 2003, leaving me with the 4 thread head. The car makes great power, and is a fast car. No problems. This thread seems to create paranoia about the heads. All ya all just need to drive, race, and not worry or spend the money to fix something that is not broke! This thread is nonsense in lieu of the sanity of people who are fixated on a problem that doesn't exist if you are smart about your driving and car maintenance. Forget what head you have and enjoy your car. Quit obsessing!