my 84 AE has had this weird prolbem for about 2 weeks now. the first week it was happening it would die any time it came to idle, i would have to pump the gas to keep it running. i fixed the prolbem of it dieing, there were 2 vacume hoses one was not tight and the other was cracked. so i fixed those. now ONLY SOMETIMES i will start it and it will idle fine and the next min it goes from 700 rpm to 400-500 and the whole car shakes. when i listen to the engine it sounds like that is a vacume leak, but i cant fine anything that looks out of place and my vac/boost gauge says 15-17 (normally at 20) when it is stumbling/hesitating. anyone had this prolbem before or knos what could be wrong and how to fix it?