i personally would NEVER buy an uprated and tuned Focus rs..or any car.
Its much better to start of with a standard car...and make it your own as you have experienced the car the way it was meant to be.
It saves you from sooooo many potentially big problems...even though a mild tune like this shouldnt be a big problem..but still....it CAN be.
And last but not least...a tuned car will most likely have been abused by previous owner...not always the case...but more likely than if the car was a standard one.

cheers.