I too was confused about 408bhp!!
I do know that a T34.48 will run to 400bhp though.
De-shrouding, is a clean up of the area immediately next to the inlet valves, as it is a bit poo here as std, and causes a restriction, no doubt intentional for emissions reasons, leaving the ports the same diametre for gas speed, but it is about 6/8 hours of work, but really effective.
I used DARREN at DAMICO, which is in EAST HARLING, NORFOLK 01953 717784.
he has many many years experience at all levels on most heads, certainly loads on cossies, n/a and turbo, has engine dynos, flow rigs, so not a guesser.
I must admit it is F*****G SCARY in the wet, I scream like a little girl!!
tabetha