Not sure if the foam pad stuck on the base of the air cleaner box is just for induction noise purposes and not for any other purpose, eg air flow/swirl?
It's been breaking apart for some time now (like a lot of the foam on this car) with bits of foam falling away and probably clogging the filter.. It's leaving black marks on my skin to the touch so I'm going to completely remove it for the time being.
Looks like it's 7mm thick, probably high density foam and stuck down with thin double sided tape.






Bits of foam missing and some of the lose bits placed for the purpose of this photo.

 

I'm thinking that noise wouldn't likely be the reason for the foam here since its quite away from the driver and its likely to be more air circulation/pressure reduction in the air cleaner box.
So off I went and peeled all the loose bits of foam out and the factory double sided tape. It was just a sticky mess and I got a lot of the foam on my garage mat and on the soles of my shoes...
There was no way during curfew here in Melbourne I was going to get 7mm foam but fortunately I had a high quality cloth backed 6mm roll in the garage.
Not much fun trimming it to fit without a template but a few hours later its in. I made sure there was plenty of high quality thin double sided tape stuck down first as I had visions of the new foam being sucked up and blocking the air filter.
There was plenty of tiny bits of the old foam that had sucked up in the air filter. So I would think if yours looked like mine, either get rid of all the old foam in the air cleaner box out completely and run no foam or spend a few hours re trimming it.

6mm cloth backed seemed to go in nicely with plenty of thin double sided tape.


Foam must reduce pressure/vortex/air swirls, who knows?


Factory double sided tape visible after all loose bits of foam cleaned out. Not visible here due to shadow in top RH corner photo but there was more double sided tape in that area. Fitting this tape and foam by hand at the factory would have taken a while to get it stuck in right. The engineers would have gone to this trouble for a reason. Not sure if foam is present in the air cleaner boxes of all the other S -Type derivatives?