check the plugs out. if you used copper plugs they are worn out. they only last about 15,000 miles.
new copper core plugs are cheap enough to just toss in, under 20 bucks.
my car did something like that over x mass, misfired stumbled a bit, had two codes pending for the icm, the next day it acted up again and stalled out, then set the light with the same codes. i cleared them and its been fine since. i did score another icm in the meantime of course so next time it acts up its getting swapped on the side of the road.
