Code PO174B Help

I have a 2003 Chevrolet Tahoe engine code Z with current code Fuel trim system lean bank 2 and a history code for the same except bank 1. Fuel pressure 44 lbs, I'm told that's normal on Z code engine 2003. O2 sensors are working properly when I checked them with scan tool. Checked for vacuum leaks, found none . Just wondering if anyone has had this problem before. Owner said one shop put a new fuel pump in 6 months ago, I think they were thinking the fuel pressure should be 60 psi. Thanks ahead for any information you folks might have. By the way that Z code engine is ethanol (flex) fuel.

Double check the fuel pressure specs.
I show 48/54 on a 02 engine.
Low fuel pressure or a dirty injector or 02 sensors can cause the code.

Hook up a fuel pressure gauge and test pressure on the road after it warms up good.
Post back pressure redings on the road.

Thanks for the information, but I haven't had access to the tahoe lateley to furhter investigate the problem. I'll post back when I do.