You have a 1/4" of movement left to go at the lever on the transmission?
If I remember correctly when I did mine, following Martin's instructions below the throttle valve lever on the transmission was completely open after adjusting the cable this way. Maybe your cable is stretched and worn out
TV Cable Adjustment:
"Remove plastic clip at throttle body end of cable.
Have assistant hold accelerator pedal to the floor, and keep it there until adjustment is complete.
With accelerator pedal floored, pull the black TV cable sheath towards the firewall until the metal wire is tight against the throttle lever on the throttle body, slowly let the cable sheath come forward about 1/8” and re-insert the retaining clip.
Have assistant release the throttle, then floor it again and hold. Check up and down movement of the wire going to the throttle lever (like a bicycle chain), there should be approx ¼” up and down movement of the wire with the throttle wide open."