My SES light just came on today and I have a P0174 code lean condition bank 2. I have 150k miles and not sure if 02 sensors have ever been replaced. I checked the vacuum leak trouble spots and have no issues there but from what I read that usually triggers bank 1 and 2 lean condition. I do have a K&N air filter so I just cleaned the mass air flow sensor and need to wait to see if the code clears itself based on some posts about P0174 due to dirty mass air flow sensors. I was wondering if it is worth replacing the O2 sensor or not.

 

Clean your MAF and if you still have your old air filter, install it and see if the problem clears up after resetting your code(s). It's not uncommon that a person over oils the K&N air filters when performing a routine service.

 

You said you checked the trouble vacuum spots but when I had the PCV rubber elbow crack, I too got the same code.
If the MAF cleaning doesn't work as suggested, I'd go back and double check that elbow.

 

Disconnect your battery for a minute or so to clear the codes, re-connect and drive it for a while and see if the SES light stays off.

 

So I cleared the code and it came back on with in 3 short trips. So I ended up replacing the O2 sensors, I did both since they are old and have 150k miles. Light has stayed out after 3+ hours of driving and 150+ miles. So I guess it was the sensor. They don't make it easy to get to the connectors for them. I also replaced the vacuum elbow on the top of the intake since it was dried out. After removing it I saw a crack on the inside corner of the 90 but I am pretty sure I did that removing it. Either way it seems to be fixed.

 

That vacuum elbow is a major cause of driveability problems and is most often overlooked during a cursory inspection. I believe that was your problem in the first place and the sensors did not need to be replaced at this time. Eventually they would, so now it's done anyway and you won't have to worry about them probably for the rest of the truck's life.
Good to hear it's on the road again.