The Echo Sportivo has the exact same engine as the Echo sedan, I think. According to Gran Turismo, there was a RS turbo version sold in Japan and New Zealand. Maybe someone sells a turbo kit. A kit would be good, as it would probably come with the manifolds and pipe work you need.
As for wheels size, you just have to fit them and see. Bit I don't see much point in going with big wheels. I would be more than happy with 15".