My '87 Horizon, 2.2 carbed has a bad surge right around 1500rpm. It doesn't matter if it's in neutral standing still, or whether you'r trying to drive down the road. If you put it in gear, hold the brakes, and give it gas, it will start surging right around 1500rpm. It's almost as if the ignition switch is being turned on and off. Once it gets to 2000rpm it runs smoothly from there on up. It will idle with no problem. New fuel filter, checked all the vacuum hoses, I've never had one do this before. Any suggestions will be appreciated.