Air mass sensor? One of the 4 oxygen sensors?
Just take it to a dealership and for half an hour labour charge they can run a short test and you can replace what is faulty. Much cheaper than throwing parts at it.
If their computer doesn't throw a fault code (but it most likely will) then you may need to leave it with them.
But try a short test first.

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Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi