GMC Repair: 2001 GMC Yukon, fuel pressure regulator, o2 sensors

Question
2001 Yukon 2wd
5.3 engine
Last 9 digits in VIN 31J189915

Engine started missing a little bit. Thought we might have gotten some bad gas. Put Lucas gas treatment in and filled up again. Started missing more and even died a couple of times. Seemed like when it was running rough, the more you push the gas peddle the more it bogged down and would die. Sometimes it would run fine for 20 to 50 miles and act up again. After the Lucas treatment I put a new fuel filter on it and it ran good for a while and then came back. Engine light did come on after it died. Code was "system 2 lean bank 1 and bank 2". I changed the front O2 sensors, air filter, fuel filter again, and clean the MAF sensor, and ran it for over 20 miles with no problem except the engine light stayed on (thought it might take awhile for light to clear). My wife got in it and it started riding rough again. Went ahead and changed the back O2 sensors.  Ran fine and the engine light was off for the rest of that day and the next morning. That afternoon it start all over again running rough and die. It will die while idling or running. My next option is the fuel pump, but wanted to get some expert advice before tackling that job.

Any help will do,
Thanks,
Joel

Answer
Hi
2 things to check first is PROBABALLY it.
The fuel pressure regulator is PROBABALLY leaking into the intake system. You can remove the small vacuum line off the regulator (small round regulator on the DRIVERSIDE fuel rail). If ANY gas is present in the vacuum line  the regulator IS bad. You can also take the vacuum line off the reg. while engine is running bad, etc.. and see if gas is present then.
Other idea would be intake gaskets.
They are common leakers and would produce lean (vacuum leak) codes.
The regulator will make it stall out, though.
I hope this helps.
Please follow back post, if needed.
Good Luck
Pawl