Sorry if this isn't the correct sub-forum for this, but I'm not asking for a tune per-se.

I'm wondering if anyone has written code to enable wideband O2 closed loop control for the 551M, and if so, if they'd be willing to sell a tune with the code for personal use.

I am planing to do something similar over winter, but something real simple. Maybe only PI controler
Also I consider option to convert ASN 3.0 ECU to turbo beacuse it already have wideband control. I will take eqsyer option

If you've already done this once, including PI, you can definitely do it in ME7, but there is no existing lambda control PI code that i think is vaguely reusable in ME7.1.  Maybe you can steal code from ME7.5

Bets of luck. Bonus points if you publish

Force fuel trim on even if lamsbg_w != 1.
Then create a mapping of wideband to narrowband based on current request.
Disable the protection that cuts load if narrowband shows lean on boost.

I think that's all that is needed, ECU should do the rest.

Well obviously you will need to handle the diags and heater diags.
And if you're using external controller, and it goes tits up and sends a fixed signal all the time, then that might not end so well.
Sensor degradation is also a problem.

So in the end IDK if that's such a good idea.
If you look at most aftermarket ECU's with wideband, none of them run closed loop on WOT, because the diagnostics just aren't there to deal with sensor shenanigans.
I certainly would not run it like that on my setup, too dangerous IMO.

Every wideband Bosch 1.8T or etc file does this. Wideband controller is disabled when certain conditions are met, too hot, BTS on etc because you dont want a faulty sensor to burn down your engine I guess.

Could put the same conditions or some of them, say if bts=1 , disable correction.

I have set up wideband lambda regulation for all engine loads, including WOT, for over 200 customers. I know for a fact that it has saved numerous engines from running lean at WOT. I do not know of a single engine that has been hurt by a faulty sensor. I have an error handling routine that will put the ECU into limp mode and  trigger a P0130 DTC when a constant signal is detected for more than 45 seconds. I have seen a few sensors fail and give an erratic reading, but most of the time their failure results in a constant output. I have found that leaning cruise and idle AFRs to around 15.3 increases fuel economy by a few %, not huge, but a nice bonus.

You guys are funny, it seems like the majority of you think that baboons are driving these cars - that a driver has no ability to detect if their is a problem with their engine. I understand advanced engine management systems have the error handling ability to decrease the possibility of engine damage to almost nill, and that you like to keep that functionality at whatever cost. However, from an automotive enthusiasts perspective, being in tune with a vehicle and knowing when something is wrong is part of the experience. For wideband control I consider it mandatory to have a wideband gauge that is easily visible, and to look at it from time to time - it is quite easy to figure out when the sensor is reading incorrectly.

With all that said, I'm not even sure how necessary wideband control is and how good ME7.1's AFR control is at WOT. I have barely started to scratch the surface with ME7. In M4.4 every lambda and VE map, including FKKVS is all in one single map, KFLF. Getting a repeatable and stable AFR at WOT open loop is an exercise in frustration, so wideband lambda control at WOT is very useful.

I am installing dual widebands on my 2.7t this week and will start logging their output through the rear O2 inputs. If I find that a closed loop wideband control routine would be helpful, then I will post my progress towards that goal here.

Cool story bro, should have started with M2.3 LOL