i dont know what to tell you. with 12 " of vac its not gonna idle right, if its a leak you need to fix it , and if its the cam you need a conv. if its a leak it shuld or will increase rpm if you choke it or spray it. ifs its not a leak it want. if its late timing causing the low vac. it want increase the rpm's when sprayed, but i hope you have the timing right.