Tuned or tuned up? Theres a real difference there. I assume that no one re-flashed the ECU for you and that the car was simply given the usual "tune up" treatment, ie. new plugs and wires, fluids and maybe they checked and reset the timing.
If you really mean throttle response and not better performance (more power) then a real tuner with the right equipment and experience can proabably help you out but unless there is something causing the motor to be un-responsive then the difference will be minute. And if the motor IS un-responsive then you have other basic issues to deal with first.
If you want true hair trigger response and some real top end gains swap to a speed density system and fabricate some ITB's (individual throttle bodies) one for each port.
Sized right and with some major tuning you'll have an SBC that'll blow you away around town.
BTW the above is a fairly involved project, you have been warned