Mass airflow sensor not emissions equipT??

I have a 2000 Millenia with 37,000 miles at the dealer right now. It has a missing/stuttering problem. Though it is out of the regular warranty, I believe it is covered by the extended emissions-oriented warranty. The dealer says the mass airflow sensor is bad and that it will cost me about $350 to have it fixed. I asked about the emissions-related issue and was told that this is not covered. Dosn't seem right to me. Does anyone with more knowledge know? And if it is, what should I do about it?
THANKS!!