@Simmon67, how are loading your engine up to determine your max boost 10-11 psi level (bypassing the VNT vac sol)?

You have done the correct test to determine if you can make boost, bypassing boost controller (vac solenoid or manual boost controller eg: Dawes/Tillix). As you realize caution is required when doing this test as you can over boost if not careful. But if no vac or boost leaks are present you should be able to make boost max to 30psi(spike) but need to hold below 15-16psi with stock ECU or limp or damage to stock turbo will occur. I recon you do understand.

As you do make boost (10-11psi) by-passing vac sol, it tends to point towards the vac sol being defective.
But you say, you cannot make boost with Diesel Smart positive pressure actuator. This indicates a possible boost leak as you have closed vac off(as U stated). Check the o-ring under the boost Y adaptor at the MAP sensor. Are U running stock inter cooler and is your cooler in good condition(no oil smears etc)?

I do not think it is your stock ECU but a remap is a good idea. Should fix the boost issue first.

With ECU remap you will most likely run max boost 20-22psi so a manual boost control kit is required. Either Dawes or Tillix, I have used both and currently run Tillix which suits. With Dawes / Tillix, the CRD can run max spool (no needle valve), suggest you install a needle to control spool rate.
You can also successfully run Tillix / Dawes in conjunction with the VNT vac sol post remap(CRD). This is what I am currently doing. Remember though your vac sol may be suspect.

I would recommend you buy a Tillix or Dawes kit (with needle valve) and get you boost under control first before remap (this will isolate VNT vac solenoid).

We can help you if required mate.