99 explorer trouble code p1131. please help!

[99Explorer_]

I have a 1999 explorer xlt 4.0 sohc with a trouble code showing p1131. I know the code points at the bank one upstream o2 sensor and I have tried replacing it with no change. it idles rough at times also stalls and bogs at higher rpm (like when merging on the freeway) i have gone over the vacuum lines over and over and cant find any leaks even had a friend try spraying starting fluid around the intake ports with no revs or bogs. im not sure what else to check please help!!!

 

[2000StreetRod]

Intake manifold vacuum lines

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1

The list and location of vacuum lines may help:
Intake manifold vacuum lines

You might also try adding a bottle of fuel injector cleaner to your fuel tank. Maybe one of the injectors is clogged.