what other things will set this code

Question

i have 97 buick park ave with a 171 code have replaced upper intake, pcv valve & seals, fuel filter ,cleaned egr, new front 02sensor

Answer 1

if there are not intake leaks or exhaust leaks, try to clean the mass air flow meter with mass air flow sensor cleaner

and maybe check fuel pressure (48-55psi at idle)

see the whole diagnostic procedures below