Not sure how long this has been happening on my 98 SE but just noticed it yesterday. Usually occurs when the speedometer hits 45 mph or so and when there a gear change. As the car slows down, instead of a steady drop from 45-0, it'll start bouncing around up and down. If I accelerate, it doesn't bounce. I have not experienced any performance issues yet due to this. Any ideas?

 

Throttle position sensor. Check this webpage out to see if you can diagnose the TPS as your problem: http://www.vbxmaxima.8m.com/tps.html

good luck