Aftermarket throttle cable

stock pedal, so first of all make sure it can mechanically move freely, not bend, nothing under the pedal

then there is the other side, the closer the cable attaches to the pivot point of the carb, the more a certain amount of move on the cable translates into movement of the butterfly

(1 inch movement in the middle of the arm might be 1/2 throttle, 1 inch movement on the top of the arm might only be 1/4 throttle)

also, since this is a cut to fit cable, make sure there is no binding there, and neither one of the ferules is causing the bind

(i could totally see the ferule in the firewall portruding to far and acting as stop (like a coke bottle that gets stuck under the gas pedal))