Check Engine Light 1997 LeSabre

Have been having a problem with CK Engine light coming on and staying on. Had Advance Auto Parts put OBD-II scanner on it and got a message that "System Too Lean". After replacing TPS and OS2 sensor on manifold and still getting CK Engine light... I had mechanic run a fuel pressure check and it showed "22" psi. He said that was far too low and suggested replacing the fuel pump. Does this sound legitimate?

Asked the shop here... They agree on 30- 70lbs.. will run but 22 sounds abnormal..
I believe a 99 buick is 50 psi @ around 25cc per minute..


GOOD LUCK