I think a Plus 4 is a good choice. Personally, I would prefer an older Duratec 2.0 because you can do so much with it. Not that this is your goal, but as I understand it, it's the very common machine loved by many tuners and brands like Caterham. And yes, the window of time between Duratec with Mazdagearbox and the release of the GDI is interesting. Below are two example links about what one forum member gets out of his Duratec. He has opened several nice threads regarding his Duratec.
