Hi guys, I don't know anything about remaps apart from the handheld units like bluefin and dreamscience etc so any help would be appreciated.

Basically can a cars standard ecu be reprogrammed to create a custom map or would you have to buy an aftermarket ecu like omex or similar.

I remember reading an article in fast ford about remapping but it was a bit over my head so any "remapping for dummies" answers would be great!

Ps, Car In question is a focus st225. Thanks!