just because the car is a Police Intercepter, dosent mean it has PI heads...PI in this case does not mean Police Interceptor, it means Performance Improved. I drive a 1996 CVPI, and my car has no PI heads, and more than likely wont, PI intake and cams? yes that it will have. And i looked it up, the CV's got the performance improved heads in 2001. so your 98 does not have PI heads. Sorry.
If you need anymore information on the subject check out
www.crownvic.net it has all the info you will need to make the determination of what you really have