Hi Darren:
I had to loosen the exhaust headers on one side of my ST 1100 a few months ago in order to get access to replace the clutch slave cylinder. I purchased two replacement 'washers' (actually big fat gaskets) to replace the existing ones, because the manual suggests that they be replaced when the headers are removed.
To make a long story short - I didn't replace them, and the moto is running fine, no leakage.
It was very difficult to loosen the bolts that clamp the headers to the side of the engine. I suggest you soak the studs & nuts as best you can with penetrating oil for 24 hours or so before attempting to remove them. When I did take them off, in 3 of 4 instances the nut came off, on the fourth instance the stud unscrewed from the block with the bolt firmly attached to it - see the second from the right in the photo below.
As others have advised, be cautious & gentle in that area - last thing you want to do is bust a stud, or strip something. If I recall correctly, the torque values are pretty low. You will need to alternate from side to side several times when putting it back together to achieve the specified torque.
FYI, the horizontal chrome piping you see in the photo below is an emissions system installed on North American motorcycles, you probably won't have it on yours.
Michael
PS to John O: All I had to do was drop the header the small distance shown below in order to get the clearance I needed at the clutch slave cylinder. No need to further remove it.
