Eivind Soltvedt: I hope you are not expecting any measurable difference in power with a re-worked air intake because you will not get any., or so little, you will not be able to fell the difference.
Relocating the oil breather will also not give you any improvement.
Unless you are ready to invest a serious amount of Kroners into your engine, do not expect any improvements over stock by modifying anything outside the engine.
In my opinion, it would be more effective and more rewarding to correct the problem you are reporting by removing the cause of the loss of power.
Start with the basics first: Compression and leak down test, Ignition system and fuel system,
jackd