Toyota Repair: 1998 Toyota Tacoma Check Engine Light PO171, mass airflow sensor, phillips screws

Question
Have a 1998 4 cyl automatic Toyota Tacoma with 216k miles. In July 2010, began to run really rough. Had plugs and wires changed. Still had problems. Come to find out, cat converter was bad. Had that changed and check engine light went off. Four months later, came on again. Second mechanic stated was a loose vacuum hose. Did fine for four days. Check engine light is back on again (PO171). MPG has dropped. How do I fix?

Thanks.

Answer
Try replacing the MAF(mass airflow sensor) in the intake just past the air filter, it has two phillips screws and an electrical connector, sometimes they can be cleaned using some electronic cleaner and spraying inside the opening where the sensor wires are, this is the most common problem for the P0171 code.