Just wanted to through this in from my experience.
So I purchased Arnott front shocks with air suspension (with or without sports suspension).
Rear bilstein B6 yellow shocks with sports Arnott airbags for the 4.8is which I found is a no go, the ride was like a stiff bouncing castle.
I researched and 4.8is does not have sports air suspension, it has comfort so i installed comfort instead.
Then the ride quality with the rear b6s was amazing motorway and whining country lanes great but slow control and little bumps you felt a harsh ish ride.
I read that the 4.8is has bilstein b4 OEM, so I purchased and installed them.
The ride was pretty much the same with regards to bouncing but the cornering was absolutely crap, I don’t remember it being like that with the OEM rear shocks on.
So I put the b6s back on and I can now corner like I’m on a rail track.
I’ve wondered if the 4.8is did in fact have b6s fitted from factory but painted black not yellow?
I wanted to tell you guys who are thinking of changing shocks to not be put off by b6s as they’re not as bad as some say but I take it’s personal preference.

My questions are

1- Is my set up of having Arnott front shocks ok with bilstein b6 rear shocks?
2- If by swapping out my rear top rubber mounts would make it better ride quality with regards to going over bumps with noise travelling through car, the ones that are on look ok with no obvious cracks or anything, or can it be the density of the rubber that is worn but can’t be seen?
Thanks guys