Cant figure out lean conditon bank 1 p0171 05 pontiac gto ls2 6.0

I have a 05 pontiac gto auto 6.0 ls2 gm motor i been trying to figure this system to lean bank 1 for few months. Whats happening is it has a slight rough idle and eventually if i drive it for about 1-2 weeks daily driving it to work and back just 1 o2 sensor goes out stays stuck on voltage reading the bank 1 sensor 1 upstream stops working when u take it out its black from running rich and you can smell the unburnt gas too.

i put in like 6 new o2 sensors every time it fails and reset the codes and it works for another 1-2 weeks. I also pulled the bank 1 plugs and they where kind of black to from the pcm making it run rich to counter the lean code i guess? I already sprayed carb cleaner and sprayed water and could never locate a vacuum leak, so I went ahead and put in new intake manifold gaskets still same issues, I cleaned the maf sensor with sensor cleaner same issue, i put in a new surge valve same issue. there is 3 bolts missing from the exhaust manifold where it bolts tot he head can this cause the issue or a exhaust little down before the upstream o2 sensor?

whats happening watching live data in scanner is the bank 1 ltft value is around 8% it goes down to around 2-4% when in around 2k rpms but sometimes it goes up high like 20% once in a while but goes down in higher rmps, also notice when i pressed down the brake pedal it went to 11-12% same if i put it in gear not in park holding down the brake it went to 11-12%.

Anyone have ideas?

Of course exhaust leaks will affect lambda readings.

Fix the obvious faults first, before firing the parts cannon

Unfortunately, you're going to have to catch it acting up to make an accurate call on this one. Based on the code (lean) and the condition of the plugs (rich), I'm going to say that this is a false lean condition.

Have you cleared the codes yet? The Freeze Frame data for P0171 may have some useful clues as to what's going on. If you've already cleared the codes, be sure to save the Freeze Frame data the next time the fault sets.

Either drive around with the scanner connected and watching data, or at least keep the scanner handy so you'll be ready.

Pinch off brake booster vac hose and see if trims are different at idle and such. Also do you hear a wooshing sound when you press the brake pedal? What is the grams a second reading of the MAF sensor at idle (should be close to 6 grams a second) in park and at 2000 rpm when driving?

To expand on what Tyler said check wiring for O2 sensor from fuse box to O2 and from pcm to O2. Visually check for shorts/broken insulation/green crusty stuff in connectors and wiring at O2 and at pcm and fuse box. Check voltage readings at O2 sensor and at pcm and see if there is a drop in voltage between the connections. I say this due to you replacing the O2 sensor multiple times and same thing happens. The other thing to check would be maf sensor signal and hertz frequency (will need a scope for this part) to check for MAF sensor drop outs or glitches making it over report grams a sec air intake. Check powers and grounds for this sensor and check data display for maf to see what grams a second it's reporting. My hunch it's in these two areas.

And yes as Tyler said fix the exhaust leaks first as the exhaust manifold will stretch and twist when it gets hot potentially causing it to think it's running lean.

The maf grams at 2k rpms is around 20 grams/s, I did buy a new maf other day and it didn't make a difference. I did put in missing exhaust manifold bolts on the driver side but that didnt make a difference I do i have a loose just hanging on the pipe a exhaust flange down in the cat back middle area but i think that's after the sensor 1 o2 so that wouldn't cause a lean i don't think right? but I need to get underneath and look at exhaust for more leaks.