Fuel trims - negative

I'm chasing a negative fuel trim issue on both banks (running rich); stock DME tuning (241E).

About -17% at idle, about -3% while driving, never really going positive. These are the long-term trims, short-term isn't significant. Seems a bit excessive. The numbers are similar on both banks.

Bad MAP sensor or O2 sensors? Leaky injectors? Overzealous pressure regulator?

Plugs changed 8k ago, already changed fuel pressure sensor, fuel tank breather valve, and donut gaskets after the header.

Is this normal? What else should I check?

I would start with looking at items that affect BOTH banks, IE MAP sensor, low pressure fuel regulator, etc.
However, short term fuel trims DO give valuable information on what to expect of long term fuel trims, so that info could be helpful.
I wouldnt say O2 sensors simply because different upstream O2s control either side of the engine.
Are you getting a check engine light with P0172/P0175, or are you just tinkering with data?

Kwike92M3 wrote

I would start with looking at items that affect BOTH banks, IE MAP sensor, low pressure fuel regulator, etc.
However, short term fuel trims DO give valuable information on what to expect of long term fuel trims, so that info could be helpful.
I wouldnt say O2 sensors simply because different upstream O2s control either side of the engine.
Are you getting a check engine light with P0172/P0175, or are you just tinkering with data?

No CEL, just reading my PID data looking to optimize my engine, trying to get trims within +/- 5%. How do I troubleshoot the MAP sensor? I have a variety of OBD scanners and software/apps including a OBDLink MX+, BimmerLink, Foxwell NT530, K-DCAN/laptop, ISTA, etc.

STFTs don't seem too wild, LTFTs are the issue.

I believe the pressure regulator is in-tank?

did you ever solve this issue? just was looking at data tonight and very negative LTFT on idle. going to do more logging and investigating when i get the chance. my injectors, purge valve, and pressure sensor are all brand new.