carb/vac issue

ok,i removed the carter 1 bbl from my 225/6.it only had two vac hookups the pcv and the vac advance.i put on a carter 1bbl that was on a two year newer car than mine for only six months.everything hooked up fine and car started up fine,but this carb has a third vac hookup that i plugged off.when trying to drive at a steady speed the car is now surging,never done it before..just hoping you guys could give me some ideas as to what might be wrong..new pump and filter was put on also and all connections are tight,even checked the ones at the tank...thanks in advance for your help...:read2: