I have a 66 w/ an I-6. And for some reason she idles incredibly high in the 1500 range. W/ out the vacuum advance i time it to specifications. Next I put the vacuum advance back on and the rpm's shoot up to 1500. I turn out the idle adjuster all the way and it still doest get lower than 1500. Fuel mixture screw is in all the way and still no change. What am I missing? Can the vacuum be to strong or something wrong with the vacuum advance or am I just straight missing something?