You are under a court order to have the breathalyzer in your truck. If you take it out early, you'll be in contempt. They can require you to keep in in another five years if they want, or suspend your license or whatever.
I have a problem understanding your time line. You've had it in your truck for 2 years out of the 5 required, you were clean and sober for 4 years. That tells me that you had it in your truck for 2 years before you were required to install it? Doesn't really matter, just keep it in your truck until you've satisfied the court requirement.