Have you not heard of kit cars etc? Have a look here:
http://www.750mc.co.uk/
How many wins do you see on there with I4?
Notice how Formula Ford uses the ZETEC and not the I4?
http://www.britishformulaford.co.uk/index.htm
A ZETEC is a ZETEC so the Focus WRC counts. Did the RS2000 win anything?
NA, up to 200 bhp the ZETEC is best engine for £ per bhp and even as you go up to 250 bhp it is still competetive.