The 1.8 20VT engine is one of favorites...I've owned, fixed and modified 5 of these in various forms...
10psi is perhaps right for standard turbo and standard mapping, if its a K03S turbo. I think the K03 turbo boosts lower around 7psi...
Also if I recall back to my SEAT days, you get various types of N75 valves, each affecting the boost level.
The standard bosch recirc valves are known to be a weak spot on these engines too, often replaced by a Forge 007P or similar.
MAFs are known to be problems as are the ignition coils, but it seems you have interchanged most of these parts.
What error codes do you see? What is the history of the car? Do you have VAG-COM to possibly read the live data measuring blocks?
Technical Author @ Pico Technology UK