im looking to put PI heads on my 2000 crown vic, with me in it, or an estimate of my Children, and wife, it weighs 4075, it has a 4.6 liter with the police interceptor package... which means 3:55 ratio. im assuming this wont make much of a hassle at the pump. But my intentions are to polish to diminish the spark knock that many tell of.... these heads maybe also be equipped with Non stock cams, and the springs look like there non stock. But fortunately i have some numbers off the cams... they read 13 on the back of em.... are these stock? cause these that came with the heads look no where near there on my non PI head cams... another thing. my static CR is 9:30.1 ratio.. thats stock. one whole point i hear can make me pump only 93 octane.. if i polish the chambers however... will this change?