my fiesta rs turbo is all over the roads at high speeds 60mph plus.its nearly impossible to keep it where i want it to go its like it has a mind of its own.when turning the steering round a steady gradual bend on a dual carriageway or motorway etc its like a delayed reaction from the steering then massive amounts of oversteer trying to force me alot further across than needs be resulting in me snaking the steering wheel trying to keep it straight again.i have given the front suspension a visual check and all seems ok.thanks!

 

have you checked your lower arm bushes with a lever bar, also the turbo arms are longer than std ones and aftermarket suppliers only list one arm so you may have wrong arm on one side throwing the alignment out?

 

As said check rack, bushes(back and front) tyre presssures, geometry, shocks.
tabetha