If the turbo is spoiling and you get 3 psi then it's starting to sound like the problem is related to a clogged exhaust. What I would do is disconnect the downpipe and lay it to the side. Use some wire to temporarily hold it in place. Take the car out. Yeah it'll be a little loud. And check the turbo pressure and see if you get anywhere near 14 psi. If the boost responds the problem is a restriction somewhere downstream of the turbo. This is pretty much a no cost check and will definitely point you in the right direction.
Be sure to let everyone know the results of your little experiment.
Roddy

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