I haven't had better than 25.1xx so not really that qualified, but I thunder up to it, then downshift one gear with a slight brake, turn hard and make it skid a bit, try to miss the curb on the left by about 1CM and then understeer out wide to the outer curb, brake really rather hard to get the next apex and then desperately try not to understeer onto the grass. It's really very difficult, but not as difficult as the next two turns.
Are you guys using the massive curb in the tunnel as a "bat stop"? I've managed to whack the curb a few times, not hit the wall and be doing about 85mph, which seems ridiculous as you go thundering towards it.
I think the key to the tight right out of the tunnel is to late apex it, you need to stay right otherwise you can't take the left fast enough OR you'll dirty the lap by doing what Kevin has illustrated that you must not do with the picture in the OP. If you lift or have to brake you'll ruin the speed up the hill and have a bad T2. Saw 24.8s just before I saved my fastest lap which turned out to be dirty on replay, then after that I blew a 45.9xx - giving up til tomorrow (or later, depending on how determined I feel
)
My only other tip is to brake late - very late - for the final turn, shift right up into 2nd and this thing engine-brakes like hell, it can make you nail the apex easier and from higher entry speed, or it does for me....
Min corner speeds:
1.) 111
2.) 76
3.) 83 (ignoring slight right before left into tunnel)
4.) 46
(... flat out down to last turn)
* Disclaimer - this advice may contain traces of amateurishness.
Edit: Had to have another go
25.137
20.827
Getting there.... not the best last turn though.
This is a fun combo for sure, and I can see spending some time on it! I don't know much I would benefit, though. I know what line I want to take, and that tunnel and I have a long history.!!! 
