There's nothing wrong with the car, or the fact that its been tracked a few times. I purchased an M3 (LMB) in October with a full discloser it had been tracked about 10-12 times. It had upgraded suspension, brakes, exhaust trim, wheels etc and those were all pros for me. Not cons. Besides, who's going to own and modify an M3 not to track it? That's what they are made for!
The issue might be that you don't have good pictures of the current condition of the car. Build thread link is nice, but current photos of every aspect of the car are better. Pictures sell cars, period. I traveled from Colorado to South Carolina to get mine. Had yours been available then, it would have been a tough call. Your color choice is very nice, but mine has more toys and they are almost exactly what I wanted in every aspect.
Take a day to detail it and post up good pictures. Showing some initiative on your part goes a long way towards tempting potential buyers. You might be surprised with what may come your way. I've told a couple people about your car, but no takers yet. Keep your chin up!