I would buy it afterwards from someplace like BMW Morristown online (25-30% off MSRP). It's very easy to install DIY. Store the factory exhaust. When it's time to sell the car, swap back on the factory exhaust and sell the MPE -- easy to do. I recently sold the Dinan exhaust off my E39 M5 before putting the car up for auction and received 80% of what I paid for it almost 10 years earlier. Stock, pristine cans went back on the car for sale.
__________________
Current Stable:
2024 G20 M340i Melbourne Red/Cognac
2019 F87 M2 Competition 6MT, LBB, slicktop, exec pkg
2007 E91 328i Silver, slushbox, Eibach fr/E93 M3 rear sway bars, ARC-8