MidwestTurboII

I drove to chicago from milwaukee yesterday with a couple of friends, and on the way down, all seemed fine. The car ran good and we cruised at about 80 most the trip. On the way back we had some light city driving (20 min or so of start and stop with traffic) then we hit the freeway again like normal. The problem is that on the way back, when cruising at like 65 or so the car seemed to pulse a little bit. Kinds like there was power, then a slight loss, then power. It also seemed like a lil more work to get from 65-75 in 5th than usual. It did not do this on the way down, nor did it seem to have this "pulse" under city driving or medium accel. Could this be a clutch thing? (slipping, maybe giving the loss of power feeling?)