Cheers Graham, it does really start to sing after 3.5k revs.
I've got video (and more importantly audio!) from all the tunnels, as well me going through in the opposite direction on my own on my way home. I just need to figure out how to edit it all together.
I was behind him at one point , had to drop back as I couldn't here my own exhaust. Well that's what I'm telling myself anyway ! Haha