I am using the car builders duo solutions pedal box. And my throttle pedal doesn't nowhere enough movement to fully open the throttle.

Has any here had the same issue and how have you resolved this.

Am guessing am just going to have to make a smaller throttle wheel to increase the ratio.

Various people (including me) have used an intermediate arm or bell crank to increase the cable pull (so it goes - throttle arm...cable....intermediate arm...cable 2...throttle).

That's easy if you've got room. Otherwise, a smaller pully on the throttle does the job - I actually did both. A good thing about the intermediate arm is you can make it adjustable to get the pull you want, I'm dead fussy about pedal travel so spent a while playing with it until I was happy.