I am still no good at making my own setups but i will learn one day lol. So i am still using inferno setups.
My understanding of anti roll bars is that for the front, not enough then there is a lack of controlability, too much then the car will understeer. For the rear not enough then the car will have body roll at the rear and lack of control with too much causing oversteer.
So now tyre pressure, the lower the tyre pressure the more grip there is, and so higher pressures less grip, that is why WR set ups are low pressure.
Taking an inferno setup for the fox the suspension, tyres, downforce etc sould be good. Now i know arb strength is a personal preference while the rest of the suspension is almost manditory for the specific track so will be looking at arb's. I have increased the tyre pressure on the fox a little to keep the temperatures down. Doing this though i have noticed that the car now understeers slightly.
So my question is how to reduce this understeer? My initial thoughts were to reduce the front arb, then i got into maybe was below the 'optimum' value so should increase it. Then onto the rear, maybe change the rear to get the slip the same. Which got me into this mess.

Sorry for the long post just like to know why the changes i have made effect the car not just what to change.

You could try reducing the front or increasing the rear ARB, perhaps try one and then the other and do a few races with it each way, see if you feel a difference and which you prefer. Some setups also have a lot of rear toe in, which helps with stability. Reducing that or setting it to zero would help the car rotate. I can't answer your question about whether reducing the front ARB or increasing the rear ARB would be better from a theoretical point of view, just say to try both options and see what works for you. You could download Bob's Setup Analyzer as that can let you know the proportion of roll stiffness that the ARBs are providing, to give you an idea of which adjustment to make. Can't find a link for it right now...

It's here

Thanks will take a look at your analyser when i have some time