The 6.2 sounds better. That's the entire argument, and it costs about eleven grand to lose it. Everybody hears M156 and thinks bargain AMG V8. What they're actually buying is a naturally aspirated engine with a documented head bolt problem and cam lobes that wear on cars that got lazy oil changes. The M157 5.5 biturbo that replaced it in 2012 makes the same power stock and about 150 more with a laptop. Here's the order to do it in. 1. Buy the 2012+ car, not the cheap one. 2010-2011 W212 E63 = M156 6.2 NA. 2012+ = M157 5.5 biturbo. The biturbo cars ask more up front and every dollar of that gap comes back the first time you don't have to pull heads. 2. Tune before you touch anything else. The M157 is boost-limited from the factory, not hardware-limited. A proper e-tune with logs on a healthy motor is the single biggest jump this car will ever make, and it happens in an afternoon with the car still in your driveway. Downpipes and an intake after, not before. 3. Service the MCT before...