The reason some engines are dirtier on one bank than the other is the PCV system design. Typically the fresh air goes in one bank, and the PCV valve would be in the other bank. The closer the cylinder is to the fresh air inlet, the less blowby garbage that part of the engine is exposed to.
Check your valve cover gaskets and see which one has the fresh air inlet, and which one has the PCV valve.
Check your valve cover gaskets and see which one has the fresh air inlet, and which one has the PCV valve.