hi, new to the board...and i need some help...ive got an 84 chevy truck i bought the other day which has a 350 in it that appears to be stock for the most part..it has a holly carb on it and i cant get it to idle smooth at all...it fluxuates badly..and has a bad histation to it..drinks gas...and is blowing a bit of black smoke...ive put the vacum gage to it and cant get it above 15 psi...the carb looks to be a 4150 model 600 cfm..vacum secondarys which i have disconected to help a bit w/gas...i have double check all my vacum lines for leaks..checked the base plate of the carb for warping...i also thought maybe the bowls might have been filling to much...cause its fouling plugs also..ive rebuilt it twice already.....any help would be great...