Does your tach drop? The tach has been dampened slightly so you may not
see it, unless the surges are longer.

It might be something belt related -- check to make sure they have been
tightened correctly and that the idler operates correctly (you might
want to get a repair manual to your car - a haynes manual would explain
how to do that).

I'd also check the connections to the battery and alternator.
If you are able, check the voltage across the battery while driving.
(you could, for instance, measure it on your cigarette lighter outlet
-- you should not see a significant change when the car surges).

Something like this could be caused by many things (ignition, fuel
supply, etc). You may want to go to autozone or pepboys as they will -
free - scan your car's computer using a special tool. The computer
often retains its error codes so, if an error code has been thrown, it
might get you a clue as to what is really going on.

Remco