For a few weeks some funky sounds have developed in my beloved 2010 T6 Volvo XC60 - approx 100K

Background: Starting towing a braked trailer with some heavy loads downhill and used 2nd gear. Never exceeded towing limits and using a braked trailer although on one occasion brake controller wasn't connected.

Sometime after I starting towing I noticed this funky sound going downhills with or without trailer. Sounds like spluttering/popping coming from upper right-hand engine bay (coolant reservoir side) - really loud. Especially increased reverse torque via engine creates the sound. Sound disappears as soon as I hit the gas or manually shift to a higher gear to create less reverse torque through the engine. Sound matches RPM of engine to some extent. Getting worse rather than better.

There was also another issue that developed at the same time. When reversing (engine cold), vibration in the brake peddle with vibratory noise which is very different from the above noise. I noted that shifting from park to reverse the engine moves considerably. Other than this, everything runs great. No fault codes on Vida.

We replaced the transmission fluid as never had done this and this made no difference. I noted a cracked upper right torque rod and have replaced this but no changes noted. Engine mounts seem to be okay with nothing obvious leaking. I pondered vacuum manifold but don't know how to test.