The stuff that matters like dynamic, electronic dampers, locking differential, etc are new on both the CLA and GLA and for that matter the A45. The power bump is actually the least important of the changes since it will hardly be noticed. At 350 a 20 hp bump isn't exactly huge and the power difference will exist mostly in the mind of owners because they know 370 is a higher number than 350. I'd bet if you had people drive one car at the old power level and another at the new power level without telling them one was more powerful the vast majority would not notice there had been a difference.
The downpipe, headers, etc methods for power increases are not applicable to what an OEM can do since they don't have the option to delete the cats or relocate them with high flow units that wouldn't sniff or pass the federal guidelines for light off. Nor is there a body of high mileage tuned cars on the road that can speak to the eventual long term reliability of the engine after the wicks been turned up. We do however know that this will be the highest power iteration of this engine and they are moving on to a new engine because they consider this one maxed out. While that doesn't tell you how much the engine can take it certainly says something about how much power MB is willing to warranty.
The lack of a 3 door surprises me especially with the 45 since its more a toy car than a tool. You have to figure in order to get payoff they would want to be able to sell 250s with it because those actually pay the bills and I'm not sure how well it sells there? Regardless I'd be all over it so my left arm could rest on the arm rest instead of hanging out in the space behind it.
