He is also wrong about the car being an M-Sport. If it was an M Sport it would have anthracite headliner and an “M” dead pedal. So it’s just a regular 2003 wagon that was customized probably before the seller got it to look like a 2003, and the seller’s BMW knowledge isn’t as good as he thinks (or Jalopnik’s for that…

Wrong, different differentials and brakes. You are sorely wrong about a 525I being similar to a 540I