I haven't done the diverter valve yet (have one on the garage shelf ready to do next weekend) but i have changed the turbo back exhaust pipe and the answer was no for this so don't see how the diverter is any different. i did find the downpipe much easier to remove from the turbo if the engine cover was off, could get at the turbo from top and bottom, this made the downpipe removal a breeze, now I have an ITG fitted, is it easier to access the diverter valve from above or is it all from below?
I did remove the heat shield from the rack which helped with access to the turbo from below.