Disco 4 Second Turbo actuation problem

Hi, I'm a newbie on here and am painstakingly trying to solve the seemingly common 'Restricted Performance' issue when revving my 2010 Disco 4 over 2800rpm. I've cleaned the turbo bypass valve (lower front right), used Turbo Cleaner in the two tanks of fuel, sprayed two cans of Turbo cleaner through the second turbo air intake, but still the problem exists. I notice that the problem does not occur in low ratio; can anyone illuminate me as to why not, and possible 'next steps', please? Thanks!

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Hello and welcome

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Buy a RangeRover.
Seriousy though I’d lay off the spray cures

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