[Overboard]

So if I can get my set up to the point where I'm seeing Max 450 up a long hill (in summer) towing near 2.5t between 80-100km/h that's a win in my books.

You will need to change turbos. At 16psi the stock turbo is putting more energy into heating the air than compressing it.

 

[Overboard]

Sorry mate, don't agree with this, my DI with stock turbo pulled good HP and did it without issues, CRD can do and does just as good. I know one that was pulling 190rwhp and 600nm torque with a std turbo.

Wrong engine. The stock turbo on a TD42 should not be used above about 12psi. ZD30s are another matter.