If you are 95% sure who it is, then you'e probably right.. There are several ways you can play this. First, you could be direct and straight up ask them if they put it there and why. For this approach, I'd ask in person so as to read their face and body language. If using this approach, I'd also arrange a time when it's just the two of you and the other person is not likely to have to leave quickly – maybe invite them out for lunch. Another thing you could do (but not near as effective in discerning the truth) is to ask them why they would do if they had similar suspicions about a GPS on THEIR car. You could also use the "asking for a friend" approach. Or, if you're into drama, you could drop a few hints that will tantalize their interest enough to put the GPS back on your car. Like "I will be going to visit a sick friend next weekend. Can you watch my dog for me?" Play all nice. Then wait and see if they do put it back on. If so, then and only then would I go to LE.
I have a family member who is a cop. From what you're saying you don't have any evidence. LE is not going to play detective for you. You have to gather your own evidence first. Or get a PI to do it for you.
Holy shit! This is great!!!
Look sweet cheeks, we already answered your questions. Stop looking for a hero cop to save you from your former lover who likely has good reason to be suspicious of you. Put on your big girl panties and be accountable for the actions that got you in this situation in the first place. Oh, and tits or GTFO.