I emailed JNL Racing to ask about head work and asked him about the issues I'm having, he said this:
When an engine is suffering from oil consumption thee is usually a quick analysis that works 99% of the time.
Smoke on startup is worn stem seals
Smoke on overun and idle is guides
Smoke under load is rings (assuming the turbo is good)
A plug as wet as the one shown on number 4 points more towards rings. This can be from being a high mileage engine or poor breather setup creating high crankcase pressures preventing proper ring sealing.
I'm now thinking the dual Saikou Michi oil catch tanks may have caused higher crankcase pressure than normal, causing excess blow-by. I have since removed the dual cans but this may have already damaged my piston rings as a result.
My engine only has 40k miles on it.
Unfortunately it sounds like a rebuild job coming up soon then! Oh well, time for some new rods!