If you're not in need of the money, and really like the car (which i know you do!), I'd keep it. Like others said, 3 years ain't that bad to store a car, it might go up in value considering what it is (last of BMW I6 6mt with very tasteful and desirable mods). What's the deal with how it's stored? Can someone come by and drive it around every once in a while?
I've contemplated selling my car but I know I wont even get enough money to replace the damn thing considering mine has a rebuilt title so it's just not worth it, I enjoy driving it too much