Looks like it's the maximum throttle point. So by default it seems to be on 50% but I guess if I reset my throttle max point, neutral and reverse again it would probably fix it. I don't think I've done this since upgrading to a 2.4GHz handset and receiver.
But as for the performance - I've set timing right down to 6deg as programming wanted to set it to 24 as default. I've then set the turbo to kick in after 0.3s. I've also reduced my punch from 9 to 7 and put around 30g of weight across the servo, bulkhead and front bumper as I found it just lifted the wheels too much to be able to steer, etc.... Kept finding the wall.
It's really awesome now - not took it out somewhere wide open yet but based on the fact it can no longer top out on my garden and is now far too fast for my garden - I'm guessing it's going to be good.
Taking it to some holiday lodges this weekend that we are going to for a works do, will take it on the golf course and feedback
Thanks for the help people.