Yer thats a zd30, I can get to 20psi safely with water meth pre turbo- nozzle.
but 18psi is good enough for now, want reliability rather than all out torque.
Only to a certain extent. Depending how high you raise it you could damage the pistons from having it to lean.
The best way to get more power out of a diesel is by using more fuel. On DI and CRD the fuel injection is ECU controlled so a chip is needed to boost fuel input.
You can gain more torque but i wouldn't say kw's.
The more pressure forcing the piston down after combustion the more torque.
But as everyone says get a boost, and EGT gauge before you do anything.
hope that helps.
if you want more power just run a chip, then you can go nuts on the boost.
the problem is they already run 15psi+ boost without an intercooler. increasing boost also increases intake heat and turbo runs less efficiently.
you need to intercool first.