MAF = Mass Air Flow sensor (box on top of air filter), at big hose that goes to turbine in place about 100mm from MAF is small hole where plastic straw (your nr2) is connected.
PTC valve - small plastic piece that connects hose from crankcase ventilation to big intake air hose before turbine, has ...

1 to T joint and from there to vacuum reservoir under left wing.
2 to hole in intake hose after MAF.
3 to PTC valve where crankcase ventilation joins to intake hose before turbo.
4 to wastegate on turocharger.
unnumbered arrow points to EGR, hose from there goes to third nipple of N75 valve on left ...

Problem is that turbo on TDI gives some pressure only after 3500rpm, at full throttle pressure is around 165kPa according to ECU live data.
Air flow at idle is twice expected value at idle an almost not changing bellow 3500rpm where it starts to rise and is almost as expected.
All measurements are ...