golden250

I know this is a weird question but I bought a car from a police auction. I think the car has a gps tracker on it, I use a wireless transmitter to play my ipod and it makes a strange noice when Im around police vehicles. How do I check for anything changed on my radio antenna or check if there is any added devices? also my music will randomly turn down around other cars. What could be causing that? There is also a weird bubble on my rear view where close to the corner is that normal? There was a trailer hitch installed as well. Please help its getting annoying and I feel my pricacy is not so private. 1997 es300