740iL stalling/eng failsafe

On a 1999 740il with 100K, I am having problems over the last month with it going into engine fail safe mode. I initially had the dealership look at it and they said it needed a mass air flow meter and this would not necessarily fix it. It had a code for MAF out of range. I replaced the MAF and reset the codes. The same problem happened. While driving you can feel it hesitating a bit and if I take off hard, it will hesitate and then go into fail safe mode where it basically stalls. If I shut it off and restart, I can take it easy and drive it. It did set the MIL again, so I read the codes and the MAF code did not come back, but it came up with P0171 and P0174 (I think) for Bank 1 and 2 running lean. I searched for a vacuum leak and can't find any. I replaced the fuel filter (included regulator) and test drove again. It is still doing the same thing, but the MIL has not come back on yet. Any ideas? What should the fuel pressure be?

I have a OTC Genesis tool that I hooked up while I was test driving. I was monitoring the STFT readings. Is it normal for the Bank 1 and 2 sensor 2 readings to never change? They stayed at 99.2%. The Bank 1 and 2 Sensor 1 would change from 0 to + or - a small number. Is there even a sensor 2 for this?

Have you had a look at the fuel pump? My E38 740iL had this problem also and it turned out to be a faulty fuel pump. - Just a thought.

That is kind of where I am leaning. What should the fuel pressure be?

I looked at the fuel pressure and it is a steady 52lbs at idle, 1500 and 2500 rpm. I looked at the ltft and it is 20% on bank one and 18% on bank two. I watched the stft and it seems to be staying at a positive number, as much as 10% on both banks, so now I am leaning toward a vacuum leak, but I can't hear one and using brake clean around the intake doesn't immediately show anything. I have cleared codes a few times and it does keep coming up with (if I remember right) P0429 for secondary air injection. I don't hear the air pump coming on when I first start it. Where is the fuse located? Which wire is which so I can hotwire it to validate the pump is good? Anyone have thoughts on the vacuum leak?

Just to update the thread. The problem was the oil separator. I replaced it and it runs a lot better... No more hesitating or stalling when you floor it!! Still having an issue with the secondary air injection though. I'll post a new thread on that.