My '87 is just not running right. Low RPMs it has no power and it backfires. Runs OK at high RPMs but it has a slight misfire (or what sounds like a misfire.) I'm thinking it has to be vacuum leak but for the life of me, I cannot trace it. I've checked all the vacuum lines and they are in tact. In fact, if I unplug them, I can definitely hear a difference in how it runs so I know they work. My next thought is unmetered air. I've tried the starting fluid trick but can't seem to locate it. Ideas?