POP is really a waist of time to leave on, you will most likely get more falses by it being on.
POP is rarely used and cannot be used to give a ticket. Its very unlikely they are using POP but if you don’t mind the falses leave it on to be safe.
The only way to know for certain if an officer is actually using POP is if you're sitting in the patrol car next to him while he does it.
hers a Video of a MPH gun with pop:
http://www.guysoflidar.com/videos/Z35Demo.wmv