I think that was the code for my OX sensors. BMW has a recall for those if the car is under 120K

Thanks guys and gals. I am throwing a MAP sensor at it in the morning. I believe the scanner issue I have is my scanner refuses to clear any codes. So the low boost code may not be immediately coming back but just appears to be. My scanner says “codes cleared successfully” but when I unplugged the MAP sensor and started the engine it set a code for that and now I’m unable to clear it as well after going through the process of plugging it back in and rescanning the ecm. We shall see. I need some good software for BMW. I am always tempted by them. When they have any lights on the dealers will unload them for unheard of prices and I can’t help but buying. I can work on about anything if I have the right software.

I second getting the Foxwell scanner. You can get the "generic" (non schwaben) version on eBay for 1/2 the price of ECS/Turner, etc. I gave my schwaben scanner away when I sold my 2009. When I got my 2013 I picked up the eBay Foxwell and it works exactly the same. Get it, you wont regret it.

Update. The code in BMW language is 4530 if that makes anyone feel better. I got a Foxwell scanner and can now reset the codes. The car will reset until it goes back into limp mode. If I drive it hard and keep it in the low pressure turbo or off the pedal I can drive it all day with no limp mode. If I accelerate slowly it sets almost immediately. I changed out the 2 EVIC ? Vacuum controllers, tested all the vacuum diaphragms, spun the turbo and checked for play, pressured up the intake tubing from the turbos to the intake, etc. I'm stumped. I do however show a constant coolant temp of 32 F which isn’t right but I can’t imagine it causing this problem. A friend of mine says pull the egr and intake and check for carbon. If it’s bad I guess it could cause issues but wouldn’t that make it run like crap on the low pressure turbo even worse?

Here is a good thread regarding the E90 3 series diesel (uses the M57 as well). Seems something in there might help you. Might need to check all of the vacuum lines. Common problem from what I've read on the forums.

https://www.e90post.com/forums/showthread.php?t=1066141

The SCR/deNOx system inefficiency code that might suggest NOx sensors is P20EE/4D16.

Your trouble code might suggest a boost leak, failing boost temperature or pressure sensors or MAP sensor. The MAFS is suspect as well. Clearly some work and diagnosis is required. I would first remedy the for-sure issue of a non-functioning engine coolant temperature indication. That will certainly cause problems and make troubleshooting more difficult than it needs to be.