2006 Audi A6 C6 4.2 V8 BAT P0171, P0174

Hello.
May name is Andrzej = Andrew in English.
Im from Poland.
I drive Audi A6 C6 4.2 V8.
Car drives perfectly fine, but...
I have those two codes P0171, P0174.
I was looking for a vacuum leaks. I found one vacuum hose with crack, then discover suction jet pump have small leak too.
Then change the MAF because it only shows max 200g/s. With new MAF it is 250g/s. Huge difference.
Finally i change EVAP purge solenoid valve. It was small leak there.
I clear the codes. Car adapts for the new values, but te code came back. Strange, because LTFT on both banks are in specification.
Both downstream o2 sensors reads  steady 0,75v. 
This is my Freeze Frame Data.  



Everything seems fine. Car starts and drive perfectly.
However, I have a car ignition lock that disengages the ignition. I have already bought the car with such an ignition lock.
For example, when I disarm it, the cruise control does not work.
But when I have the ignition lock inactive, the cruise control works the second time the car is started.
Could this affect the ECU readings some signals from sensors? 
Or it's just an ECU software bug or I'm missing something?
Best regards Andrzej
 

I doubt your ignition lock is part of the issue? But it's hard to say without seeing how it's wired exactly.

The problem with Volkswagen/Audi is that fuel trim issues aren't always reflected (or reflected accurately) in OBDII data, which is what you're looking at. In other words, it's possible for the vehicle to have a fuel control problem, but the OBDII data won't show it.

For any VAG vehicle, I highly recommend VCDS. Nothing else works nearly as well. If you're not a repair professional, and this is your personal vehicle, one of the Enthusiast packages would be perfect:

store.ross-tech.com/shop/vchv2_ent/

The good news is that the Freeze Frame data usually is accurate, so you've got a starting point. The code setting during a hot idle definitely suggests another vacuum leak. How are the PCV hoses? If you have a vacuum gauge, start the engine and install the gauge in the dipstick port. We want to see around 1" Hg.

Tayler, thank you for your reply.
I have access to VCDS. The data from it coincide with the data from the application.
Both the PCV valve and the hoses are fine and there is a small negative pressure in the crankcase.
I'll check it carefully tomorrow with a vacuum gauge.
P0171 and P0174 appear randomly. At different engine speeds and different engine loads. Sometimes after 10 km, sometimes after 150. There is no rule.
I have a slight impression that the O2 sensors are a bit lazy. The car has traveled nearly 230,000 miles and the O2 are still original. When I was looking for a vacuum leak, I checked with the brake cleaner. When I sprayed directly into the intake there was a response from the STFT but it took a little too long in my opinion.
I will also look for another vacuum leak. The TB gasket area comes to mind. I will look for and let you know what I discovered and what the logs showed.
Best regards Andrzej

Update 27.09.2021 I did a few rides over the weekend and the DTCs cleared themselves. But I did notice that, right after a cold start, the o2 shows a lean mixture and when it turns into a closed loop the mixture stabilizes.
 

The commute log also shows that when the engine is cold, the STFT rises sharply and the LTFT rises. After some time, the STFT drops and the LFTF remains constant.
 
 
 
 
After about a minute or two when the engine is more hot STFT becomes negative and decreases LTFT.
It can also be seen that each time the throttle is opened on a cold engine, the STFT drops.

Looks like a classic vacuum leak on a cold engine that seals when warmed up.
This applies to both BANKS
Or o2s need longer warm-up time to work properly.
I looked for a vacuum leak today but Break cleaner detected nothing.Maybe I'll have to make a smoke machine. No workshop in the area has it.
Here is a graph of how STFT behave on both BANKs.
 

For the sake of clarity, today's commuting to work was on LPG, but on petrol the LTFT & STFT behavior pattern looks exactly the same, only the LTFT values ​​on LPG are a few (2-3) % higher than on petrol.

Here is a log with how the car behaves when started on a warm engine.
 

What, ladies and gentlemen, do you think about this case? The classic vacuum leak on a cold engine or maybe the o2 is slowly getting enough.
No other symptoms, no misfiring, nothing.

A few days later......

My problem, as it turned out, were the previous owners of the car.
Instead of replacing a relatively cheap part, it is better to stick it together ... !#$#@$^%#$
The problem was the PCV valve.
 
As you can see in the picture. Oil leaked in the place of gluing. After replacing and resetting the DTC, these are the adjustments on Bank 2, Bank 1 looks the same.
 
I think we got a fix.
Thanks for the suggestions.
Best regards Andrzej