[mb135is]

135i is not a good choice for a regular track car just based on what you get with an E46 M3 compared to the 1er. You can make it compete, sure, but you're starting at a better track product with the M3, hands down. I would quote everything pixelblue said, but you've already read it. Take it from someone who's put the 1 through its paces.

I will say this, though - I take my cars to the track and was just in the market for something new. As always, the E46 M was in the picture, but the bottom line for me is that for the amount of track driving I do (maybe a few days per year), a used car with no warranty and _some_ miles (and possibly someone else's headache) was not worth it. I'll limp around the track in my 135is, water and oil overheated, rear brakes cooked from the fake LSD, swaying though the corners with my heavy sunroof, cozy in my heavy leather/heated seats, losing steam all the way to 7k rpm, and I'll love every second of it because that's why I go to the track.

Hell, most fun I've ever had on the track was in my Cooper S. Talk about not an ideal track car!