Having lubricated the throttle cable to take away the “sticking” I checked whether I was getting the full throttle opening when my foot was down to the floor which still had a good 15mm to go before hitting the stop on the throttle body.
There is no obvious adjustment to take up this slack so I used a rubber washer about 3mm thick to add a little more packing where the cable attaches to the foot pedal. I put a slit in it to slot around the cable at the top of the foot pedal ……. which did the trick.
I guess an alternative solution is to modify the throttle cable support on the throttle body by slotting the 2 mounting holes …… it only needs about 3mm. Surprised there was no adjustment built into the throttle mechanism.
NB this is on a V8 – other variants may be different