Surging Problem
 

I have a 88 N/A with about 2300 miles on the rebuild. I first started noticing it tooling the car around at about 35 to 40 mph. It seams to be surging, don't know of a better way to explain it. Not like a miss but more like a pulse?.?.. On the way to work this afternoon it started doing it at hwy speeds, thought it might be the cruise but I took it off and it was still doing it. I just changed the plugs last weekend and am thinking it's the fuel filter but other than that I have no idea.