£4k for 400 is do-able.
Cheapest way would be to buy a new ej257, slap some sti5/6 or P1 heads on it, get a decent blower (20g should get you there), a set of 550's or bigger, uprated fuel pump, fmic would be a good idea, headers and exhaust and then a remap.
Not sure about the 2.2 engine option, depends what you mean. Is it a ej22 or ej22t or a stroked ej20?
It can be done on a 2.0 of course but a bigger turbo would be needed to make sure you hit the big 4.