That stage 8 thing may create a clearance issue as well. some of the studs on the manifold or turbo have very little room around the heads… not enough to get the box end of a wrench around sometimes.
with a cotter pin and that thing aint going nowhere i think they use them on helicopters to keep nuts from vibrateing out under the power of the rotor blades…
I flattened one side of the threads with a;
vice grip,
hammer and flathead screwdriver…
in addition to slit washers, and the proper locking tab plate.