You may have an issue, but I have the same one.
I have driven about a dozen Panteras. I have found gas pedal movement from very soft to pretty firm, such as mine. I, too, have some long-term driving fatigue issues.
I have a newly installed (about 3 years ago) factory cable, the style with the built-in return spring at the carb end. Old cable, new cable - both felt the same. Short of cutting a loop or two out of the carb-end return spring, I can see no other area to adjust to reduce the pressure.
Larry
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