Yes well, i've never seen the pistons from these motors - hence i have said so numerous times. 7psi is about average factory setting for alot of older turbo motors. 11-12psi is limit of skylines with ceramic turbine wheels, else they break... but if you say that 15psi is average, go for it.

If you would kindly notice: i did say that the motor will get stuffed if the tune is wrong... but excessive pressure/force on the pistons can also cause failure.... you shall be stressing engine components beyond their designed loads - but these loads would have a safety factor when designed/built, hence why you can alter the engine, and not have these components fail.

Size of turbo: larger turbos flow more air. More air means needs more fuel for same compression/boost compared to a smaller turbo - less flow, less fuel needed, same boost. Is what i was saying.

High compression can cause rings to go, as pressure can force it's way past, or can crack ringlands. You seem to have stated that the ringlands must be rather well spaced and it is not an issue for these motors... ok...

I would *NEVER* base a judgement on the fact that it's a german engineered motor. Not saying that the engineering is bad; but they made the motor to be a 2l n/a motor, not a 300hp turbo motor... and thus if you shove a turbo on and run 300hp... it was not designed for that, as such a design would cost more to build, and thus you are putting stress on engine components that was not meant to be there... so obviously the engine will not last as long, regardless of the tune...