This is something we keep saying over and over, 99% of boost loss is due to a damaged hose, be it boost or vacuum as the cause. Splits and cracks have a habit of being in the places most often missed by a cursory inspection. A thorough inspection is free and can work wonders.I came across a guy in the middle of nowhere a few weeks back who said he had lost all boost.
He said he had checked all hoses etc but I looked again anyway and found a 5cm split in the intercooler intake hose.
It was directly underneath in the exact middle of the hose. You have to check the whole hose not just the fittings.
I saved him a $1500 tow fee They had concluded their turbo impeller had shattered due to changed noise and their boss didn't want them to drive it thinking it'd kill the engine.