Audi 1.4 TFSI EA211 Misfire cylinder 4

A short while ago I had an Audi Q3 1.4 TFSI EA211 in for a misfire and thought it would be an easy fix Friday afternoon failed Coil-On-Plug.

Coils all OK, sparking well on all, plugs all fine, injectors all fine.

Misfire on Cylinder 4 remained a mystery. The vehicle was fitted with a Cylinder-On-Demand technology but this only works on cylinders 2 and 3. Also had variable timing on the inlet cam. An Audi tech claimed issues with this cam timing variator could show as a single cylinder misfire but I’m not convinced as in theory the whole bank should have skewed timing.

Anybody had experience with this? any diagnostic tips on condemning/ruling out the variator or other valve train issues?