is it normal for one of these things to go bad after 21k miles cause mine is just being all loopy. casuing the engine to be really jumpy have power then bog have power then bog?
Clean it with MAF sensor cleaner before you buy a new one. They will get dirty and you'll get bad readings. Especially if you are using an aftermarket oiled filter.
your MAF is covered under the 5yr/60,000 mile warranty....if you have a stock intake system and stock air filter. Otherwise, clean it with HIGH POWER brake wash and then blow dry with compressed air.
Get some CRC automotive electronics cleaner from Autozone and try that first. I normally pull mine out a couple times a year and spray it down. This stuff is magical, a buddy of mine bought an S13 with an SR20 that was billed as "unable to idle for unknown reasons" so he got a good deal on it and limped it to my house; we pulled the maf out and sprayed it and the car ran like a charm albeit with a minor boost leak.
Advance actually has the CRC MAF sensor specific cleaner. Not sure what the difference is. Just spray the sensor real good, let it dry for about 10 minutes and you are ready to go.