Replaced Timing Belt In 96 Ls400, Now Dealing With P0171 Sensor Too Le

[bo-hio]

I had the timing belt replaced last week in my 96 LS400 @ 150K miles (90K miles after original replacement @ 60K miles). While the front end was open, I also had new spark plugs, distributor caps and rotors installed (along with a new fuel filter). Since then my check engine light has popped on several times, each time with code P0171, System Too Lean, Bank 1. Since I've already replaced both O2 sensors on Bank 1 side within the past year, I'm hoping this doesn't involve them.

Has anyone experienced this same issue following a timing belt replacement and/or tune-up? By all indications the car runs fine, though the mileage may have dropped 1-2 MPG since the work was done.

Any advice/recommendations would be greatly appreciated.

Thanks