Rpm osillation during acceleration

I have an 01 GT and sometimes when the car is running about about 1600 rpm it will begin to jump to about 2100 and back down again very quickly. Giving it a little gas or brake always makes it stop, but i was wondering if anybody knew what this might be. And for those who think i may be twictchy, the car does this on cruise control also.

come on guys help me out, do i need a new fuel pump or is my electrical system going crazy or what?