Can you help to troubleshoot this issue...?

Watch this space (as they say).

Crossing my fingers for you

 

Fuel system cleaner is mostly a band-aid. I would have my injectors cleaned and resealed with viton. Had to do it on mine.

 

Wouldn't you need a flow tester to make sure they have the same flow?

 

You could almost certainly do an injector clean project yourself but you'll probably need an ultrasonic cleaner. I think they're a couple hundred bucks and would probably be useful for cleaning parts other than injectors. I've considered getting one myself and probably will next time my 456 needs injectors cleaned...
good luck - keep us updated please!

 

You would need a source for the viton seals, too, to prevent them from reacting to alcohol in our fuel. A lot of specialized equipment for doing this and testing results, so probably easier to just have a pro do it for $20-30 per injector.

 

Apologies, on further investigations it seems that some of the plugs on bank 1 - 6 have light grey deposits too. So, other than a couple of black plugs the remainder were light grey with some deposits. The car has 60,000 miles and I’ve been using a fuel additive recently.

I will order 12 new plugs.

 

Post pictures of the spark plugs.
Cleaning the injectors without testing them on a dedicated flow bench is not enough. Ferrari injectors seem to get particularly dirty over the long term, at least mine and other owners' did, and mine required much more time in the ultrasonic bath than the tester initially thought was necessary, as he initially observed by testing them on his flow bench.

Anyway, by the sound of it your fuel pump supports seem original and in your shoes I would replace them before thinking too much about anything else.