MOT place has got a new emissions machine. It does it by the book so it starts with a BET test, I had trained them to skip the BET and go straight to "non CAT". BET test has high idle test. One way valve can't make PCV valve suck on turbo with reduced manifold vacuum and some blow by.
Makes smoke like a battleship smoke screen if held at 2-3K rpm.
Take the inlet trunk off the throttle and it runs clean.