You know the OBDfusion app on an iphone or android phone along with an OBD2 wifi reader Is really a fantastic tool for measuring fuel trims and diagnosing fuel trim related problems.

I have four BMW's with the M54 engine and I have used it several times.

The folks on E46fanatics are all over this tool. There is a whole write-up on how to set it up, capture logs and how to read the output...

https://www.e46fanatics.com/threads/...-jfoj.1097893/