Quick lesson in turbochargers, most people believe they produce boost all the time, BUT thats ******** they may shift air but nowheres near enough to produce meaningful boost, the engine has to be pulling ie driving, any squeals/rushing air means you have some sort of leak between the turbo and the inlet manifold, hoses are the favourite.
Even a small leak can make a lot of noise, but the turbo is still making enough boost so as you say its still drive okay, but and theres always a but, the turbo is now having to work even harder to make the boost so the leak needs finding before anything else goes wrong.
You can get a cheapo gauge and a t piece to check the pressure.
But if its making a noise it should be obvious, the hard bit is finding the split hose.
On the land rovers the one nearest the turbo always failed first as it was subjected to the most heat, ie pre intercooler
Wait till motor is cold and feel up each hose giving it a good squeeze! to feel for any splits, or bits that obviously feel wrong i have had a couple delaminate on the inside but looked fine outside
Lynall