Question on Turbocharger Wastegate Testing

I have the dreaded code 2885 boost deviation fault. It is easily duplicated after clearing the fault. In 3rd gear at 4000 rpm code will come back and go into limp mode. I have replaced the turbo I had very loose exhaust housing wastegate problem, checked vacuum source to wastegate diaphragm, bypass valve, decarboned valves, checked valve timing,smoked intake,pressure tested intake all with no results. I tested back pressure in exhaust at front o2 sensor it measured 3.5 psi at 3500 rpm in 3rd gear. What am I missing? 2885 is the only fault I have. Could I have a failing pressure sensor? Software problem? It is 2009 jcw thanks. Any help greatly appreciated

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This post was auto-generated based upon a question asked on our tech article page here: Mini R56 Testing the Engine Turbocharger Wastegate | R56 Cooper S Hatchback (2007-2013), R56 Cooper JCW Hatchback (2009-2013) | Pelican Parts DIY Maintenance Article

[Nick at Pelican Parts]

back-pressure is too high. Should be 0.5 psi or less.

- Nick

[Warren28]

My 2885 was fixed by replacing the vacuum lines between the wastegate actuator, vacuum reservoir tank and vacuum pump. It's a set of tubes all sold together. It seems like one of them was getting very soft and collapsing (perhaps). At the same time I also replaced the Pressure Converter p/n 11657599547, so that could have been it too. But part of those lines were practically like a marshmallow.