System Too Lean?

[994x4Sprt]

Ok. So I got my O2 sensor problem fixed but not even a day after my CEL comes back on. This time it's sayin system too lean?? The code is P0171 (Bank 1). What's up with this? Anybody got any idea?

 

[spindlecone]

Most likely a Vac leak, intake manifold gaskets, O rings, cracked hose coming from the PCV valve. Get a can of berrymans carb cleaner.
With the engine running, spray a little on suspect areas, when the RPMs change, you found the leak, if thats what it is.

 

[994x4Sprt]

Ok so use that to check all those things listed above? and where would the o ring be located at?