I'll try to explain:
The cable mount on the inside of the pedal right..hooks in from the front, opposite side of the pedal arm to the firewall.
So take off the cable from the pedal, put a spring over the cable, then a washer (cut a slot in it) over the cable so that you could hold the bottom of the spring, and the 'top' of the spring (and washer) would be up against the end of the cable (where the mounting ball is)
Now place similar washer on the 'bottom' of the spring, and replace the cable, with the spring on the driver's seat side of the pedal. Now the spring, remember, is weaker than the main spring at the TB. So when pressing on the pedal, both the spring compresses and the cable pulls, but the compression of the spring is 'using up' some of the pedal travel that would usually go directly to the cable. If the length of the spring is correct, then the spring would be fully compressed at 1/2 throttle, at which point it would be a 1:1 ratio again.
This is purely theoretical, and will take some experimentation with different springs, but it is acheap enough effort that it may be worth while.
Tim