I know that when I had those issues with my m140i BMW were pretty relentless (if ultimately unsuccessful) in diagnosing the issue, including giving BMW Krautland remote access to the car to look at various parameters. Also, bear in mind you probably wouldn't be in the first 1000 people they've seen turning up with a mystery cooked engine and out of whack MAP parameters, I bet they're pretty keyed into what to look for.
All that said, the first day after the warranty ends, I'd go for it. The way I look at it, paint correction, a top level valet and a remap is cheaper than getting the latest updated version of the model and it will make it feel like a new car.
Apparently my yank tank has an extra 100bhp and 100 lbs/ft available if I invest in a remap and a bigger intercooler. I'm waiting until the urge to upgrade takes me, and then I'll get these done.