Isn't 400 supposed to be the number that gets stock internals grenading out of the block? Oh I know all about popping spark plugs. I lost #8 a few years back and had the guys from blownoutsparkplug.com fix the head. In retrospect I should have done the PI swap then but I hated the car at that point. So, if I purchase a set of heads I should ask if they are the later, revised heads? Are the brand new Ford Racing heads from vendors like Modular Mustang Racing or Blue Oval Chips the revised heads? I wish I could buy the Trick Flow stuff but I just can't swing it. Question: since I live in Commie-fornia I have to be smog compliant. Does anyone know how this PI stuff will affect my emissions?