When I am driving on the highway, I have to speed up/slow down because of traffic (otherwise, I use my cruise).

When I slowly let off the gas, my car acts as if it is out of gas and drops power for an instant. Then everything is fine. I can sit there, increase the gas, and then let off slowly and do it almost everytime. I don't notice it happening in the city.

Any thoughts?

BTW, it is a 2001 2.2L 5-speed manual Cavalier.

Try some injector cleaner... as a first step..

I agree with STYLEZ24, try some injector clearner first. It would also not hurt to check the condition of your spark plugs. Your car is 3 years old now, you may have some deposits built up. What is the mileage? If you're over 50K, it wouldn't hurt to clean them real good or even replace them.

Sorry. Neglected to say all this info:
I noticed it really bad right after a fresh tank of gas, so I thought maybe it was a bad batch of gas w/ water in it??? I bought some stuff that is supposed to take the water out and also threw in some injector cleaner. I have gone through that tank and 1 other one after that. I just filled up again Friday PM, so if it was just that, it should have been resolved. I'll check the plugs, but I would think that it would not matter whether I am on the highway or in the city. Mostly at higher speeds (in excess of 50). I have just over 40K right now.

If plugs become fouled it can cause loss of power. You engine is smart enough to try to adjust for certian things. Pull one plug and check. It should be dry with a little carbon build-up. If it is wet, oily or has excessive carbon build-up where the spark is generated, clean or replace them.