My 2018 290 with GPF pops and bangs big style on over-run when downshifting in sport mode. I also get some some juicy farts when pushing it.
My car has 9k on it now so I think the exhaust needs a bit bedding in.
When I set off in M1 then change to M2 at about 3.5k revs I get a deeply satisfying low fart/grumble.
I've never noticed it stopping after a while. My car seems to do it all day if you're in Sport/Cupra mode. I tend not to use Cupra mode due to the intrusive Soundaktor. I'll eventually physically disconnect it!
I have a 19plate Cupra which has around 1700miles on and mine doesnt have this problem, i get loads of pops and bangs on over run and also when revving stationary, it also dsg farts when booting it, as above the pops and bangs always happen around 2.5-3k revs and dont stop until i turn the engine off or put the car back into comfort mode
I have had the odd burble and pop in comfort mode but that was only with the gearbox flicked into sport for a quick overtake.