right, the red top c20xe is an n.a 150bhp engine

the c20let looks the same but has a turbo and makes 204.

The accepted stage 2 tune on vauxhalls is about 280bhp and the limit of the standard turbo.

If I wanted 350bhp Id be going for:

Cheap steel rods - 200 quid
Machined standard pistons, 0.5mm oversize - 500
rebored block with oil squirter jets - 150
new oil and water pumps - 70
Standard head, valves etc
Xe n/a camshafts, retard the inlet
You can modify cheapish 200sx manifolds onto a new flange - 150
GT28RS - 900?
you can probably manage on a standard inlet manifold
vxr injectors - 70

Ad to that intercooler and pipework, some aftermarket management etc etc and it soon mounts up.