Not really sure if the ST170 is any good, never seem to make anywhere near 170bhp, parkers say 0-60 in 7.9 which is ok, reckon if you are going to do a conversion just get a complete mk1 focus rs engine and swap the lot over, that'll give you over 200bhp and potential for a lot more, and if you can find a crash damaged car you could strip a load of bitsd off it and sell them to get money back.