It’s not a case of it being standard or modified, it’s just an effect of crank case ventilation. It usually gets worse for multiple reasons combined. Old/worn rings allowing more pressure in the crank case, more boost pressure, contaminated breather system or a blockage.
It’s pretty common for the oil traps in the cam covers to become blocked with oil sludge and contaminants causing a restriction. Might be worth checking these first as they’re pretty easy to access.
Sent from my iPhone using Tapatalk