I have a 1986 Nissan Pulsar. It runs rough at low RPMs (lurching, hesitating). Like the air to fuel mix is off. Too much air. I have had the carburator rebuilt, the timing belt replace, the vacuum lines checked and replaced and the valves adjusted. Nobody seems to know what the problem could be and I'm going crazy and getting poor. It has 72,000 original miles. If you can help me, I'll love you forever.