2002 Neon Losing Power

I just bought this car 3 days ago (from a dealer), and all seemed fine during the test drive, and on the way home (there were no freeways around during the test drive however). Of course the car is As-Is, so I dont really know what my options will be, but the dealer has agreed to look at it for me anyhow.

When I get up into 5th gear (and occasionally in lower gears), going from about 50-65 is really jumpy, and the car seems to hesitate a lot. Once Im up to 65 or so it seems to go away, but it will intermittently come back as I drop in speed and need to speed up again. The last time this happened it took 5-10 seconds to go from 50-65 and the engine light came on for about 3 seconds, then went off when the problem went away.

Any ideas?