Having a bad hesitation problem with 1986 GN. It starts and idles fine but if I get on it at all it just hesitates and sputters. It will run but I have to use the gas pedal very lightly and ease into the throttle very slowly. I changed the fuel filter, air filter and plugs and wires. I have read that it could be a vacuum problem or the coil pack needs to be changed. Any suggestions.