Other posts have covered what a GDI engine is but to answer your 1st question.
The Plus 4 has had a number of engines with the 2 litre GDI introduced in 2014 and keeping that engine until the traditional Morgan was replaced by the BMW engined CX Plus Four. Before the GDI the Plus 4 had the 2 litre Duratec engine and others before that.
So a GDI Morgan is a Plus 4.
