Now that you replaced the MAF you'll probable start getting O2 sensor trouble codes
.
This seems to be the pattern. First the MAF, then an o2, then another o2, then another o2, then the last o2.
When you do get the o2 code...save your sanity and replace all 4 at the same time. A bit pricey, but worth it. Can you tell this happened to me on my 2000S at 45,000 miles???