Thanks everyone, I traded in my gen 3 which started without high revs. I think most modern vehicles rev harder for a few seconds on cold startup but I think it is to get heat into the cat(s) for emissions!
The issue was more with the lumpiness on startup that Eddie referred to, its slightly better when the baffles are in but still sounds unwell for a while. I've done a lot of reading that and found that the gen 4 runs quite lean at low revs so imagine with the full system on this is made slightly worse. The bike behaves on cold start-up like an old car the you haven't pulled the choke out and you're trying to rev it to stop it from stalling. After the 10 seconds or so it starts to come down but I normally let the bike idle for a good few minutes now before riding it.
It sounds like others experience this which is reassuring.
