The explanation of the demise of the turbo doesn't make any sense.

I'm kinda guessing about the turbo. The fact that when it went in the turbo was alright and when it came out after the new head and intake it kept 'overboosting' abd bringing up an error. Any gear, any revs... :(

In your first post you mentioned it was underboosting, but above you say it was overboosting. What was the fault code? Charge Pressure Control: Negative Deviation?

Let me have a look, i'll get back to ya. The under / over confusion is probably mine, i'm no mechanic