97 lesabre need some help, CEL on

i have a 97 buick lesabre i have a po171 code its system too lean (bank 1). i checked the air filter and its clean and pretty much new.. i sparyed some air intake cleaner in the throttle body and got no result. anybody have a idea where i shud start looking.... ive got till the end of this month to get it inspected so i cud use ne ideas fast. thanks.

Dirty injectors, low fuel pressure, any leak behind the maf, recently replaced pcv with the o ring missing, dirty fuel filter, are some possibilities. I assume it runs ok?

Contaminated MAF sensors can also cause lean conditions. Cleaning the MAF sensor requires removing it and cleaning with an appropriate cleaner.

"Appropriate cleaner" means; do not use brake cleaner, or carb cleaner on the MAF!