2000 Jetta running lean

I have a 2001 Jetta, also with the 2.0 engine. Mine has had the check engine light on for about 2 months now. I get the code of p0171, saying bank 1 too lean. I was told by the folks at several parts stores to change the o2 sensor. When I saw how expensive they were I had to think about it first. I actually took mine in to get a diagnostic testing. Outcome is that it is the Mass Airflow sensor. If I let it run too long with out clearing the code on occasion, it will start to throw other codes. You might want to check into that. It is really easy to remove, so it is a do it your self project.