Well, the 77 euros was expected to go to the firefighter, one paca the technical knowledge hahaha. Well more seriously, before taking out the turbo, why don't you try a pistolite of these like that of the Mitivac brand, which makes pressure or empty to see how the turbo's waste-gate is? If you don't have this gun, you can try a syringe of the big plastic that they sell in pharmacies, it is not the same, much less but good. Another thing before taking out the turbo, I don't know if the turbo of that car is controlled by some solenoid valve, or if the turbo is self-set with the same Waste-Gate (the discharge valve). If it has a solenoid valve, it is possible that it is wrong and it is guilty.
From the flowmeter I would ask you what brand is, Bosch, Siemens or which and more specifically, what car we are talking about.