i have an 88 vert when i start it it wil rev up to 3k but will only cut down if i hit the gas , i let it sit at 3k to see if it would cut down but after about 20 seconds blue smoke started pouring out from under the hood and it was still at 3k but if i hit the gas it will cut down to about 1000 and then surge anywhere from 1k to 2k after it is warm if i rev it up it will settle to about 800 until i give it gas again then it starts surging again, i onll get the smoke if i let it idle at 3k , it doesnt smoke as i drive , is my motor in need of a rebuild or is there something i am missing , i have been unable to find any vacuum leaks