It was not a mod specific to CX or any airline, but as part of the manufacturers in service 'product improvements' the pod 'angle of dangle'
was altered to improve efficiency. (this is certainly true for the RR powered aircraft!)
It was noticeable on BA's last classic delivered (DXP) and was of course carried over to the 744.
I'm not certain but it was about 5 deg nose down and was to better align the airflow into the intake in the cruise condition.
There is one airline with a 'modded' pylon fitted to the no3 position because they broke the original and there weren't anymore available. The crew would not notice any difference but the SFC for that particular engine would be a tiny bit improved.