Yes, you need a better code reader...There may be codes that a p code reader are not pulling.

you need a code reader that can read BMW codes. Foxwell's seem to work. INPA, BMW Scanner.

I use an old Peake R5/FCX3 reader...it is clunky and out of date. It requires you to look up numeric codes in a related code manual, but they are cheap used and do read /reset BMW-specific codes. Peake is also out of business.

Sounds to me like you might have some vacuum leaks, but that's a wild -assed guess...Don't throw parts at it.