carb adjustment

i tried with engine off they seem to be open just about quarter of way before i touch them, them when i stick screw driver in i can open them all the way. but dont open all the way with wot engine off. i tried tightening the throttle cable to get slack out but when i do take the slack out i lose alot of peddle travel on inside then i put alittle slack in it and my peddle travel comes back. let me throw this at you somebody before me had put aftermarket lokar kickdown linkage on it and the braided cable is frayed and loose where the adjustment is on it so i adjusted it at the little set screw it has that changes shift patterns but no passing gear could this aftermarket lokar be junk and will that have something to do with 4 barrel not opening up? i am truly thankful for your help thanks