dawes and needle valve for common rail?

[phdv61]

Don't get me wrong.
I am not saying you do not need to have more boost to get more air in.
But boost is not all. What you need is to maximize the quantity of air getting in your cylinder, as measured by the MAF voltage.

There is not limitation at 16 psi boost on the Di. The MAP sensor is not used.
I can get 20 psi if I wish, although, beyond 18 psi, the increase of air you get is little are you are getting beyond the efficiency zone of the 2052 garett turbo.

Getting a lot of boost down low is only creating backpressure, and little air is coming in. In other terms, you reduce the power/torque you can get from this engine. If you let it 'breathe' properly, it becomes another "animal".

To move the 2.5T, you need torque down low, which you don't get if you keep the vanes closed too long, and beyond what is needed to get the initial turbine spin. You need to free the exhaust gaz, or you build too much back pressure preventing the cylinders to get rid of the exhaust gaz, making room for more fresh air + fuel. And you have reduced torque and ... driving pleasure.