As you lower an RS Turbo, the amount of front-wheel camber increases. In simple terms, camber is where the wheel effectively leans in or out at the top, depending on whether the camber is positive or negative. This basically means that less of the tyre is on the road. What this results in is increased tyre wear. More importantly though, you will have less grip. If you imagine your tyre at, for example 195mm width. If you had 'X' amount of Camber (wheel leaning in at the top) and as a result only 2 thirds of the tyre was on the road, then you have lost 1 third of your potential grip.
The effect of having correct camber is increased tyre-life, better grip & less torque steer.
On a track car, slightly higher Camber (more angle), therefore less tyre on the road is a good thing as although this reduces straight line grip, as you turn heavily into a corner, the 'lean over' effect will put the tyre on the track and therefore give you more cornering grip.
Make sense??
If you decide to get a set of adjsutable TCA's, just make sure that they are good quality, made from brand-new genuine Ford TCA's and that you have your alignment set by someone who is very competent.