I just replaced the o2 sensor in my 1998 5.2 and the code po171 came up it says system lean in bank1 i was wondering on what it could be and the fixes for it

 

Im thinkin it could be a vacuum leak somewhere in the engine. Try lookin around by sprayin throttle body cleaner to see if you can notice a leak. Once had this happen on a car i was fixin and it was the pcv hose which had a huge hole right in the middle just replaced it and problem gone. Also helped that i cleaned the maf but these cars dont have a maf.