I'd also be interested in hearing opinions on the natural gas CVPI's.
While working as an LEO I drove a lot of different crown vics, but
none of them were the natural gas models.
Since you are from NC you might be interested in the following link :)
A friend sent it to me a while back, and it deals with the procedures
needed to refuel the NC Public Service Natural Gas Crown Vics....
Kind of interesting..