Frst of all i'm new to working on anything under the hood. I bought a 85 chevy silverado that needed some work. Bought the haynes manuel for it. Started by checking all the basics. Had the carb rebuilt with mixture screws set at 2and ahalf turns out. Replaced all vaccum hoses,dist cap,rotor,spark plug and wires.set timing to 4 degrees BTDC . Starts and idles fine but when driving i cant accelerate fast or up hill, hesitates (i think misfires) and blows black smoke.... HELP