Ducati Diavel Workshop Manual page 587

Exhaust system
Refit the exhaust by-pass valve cover (27) by starting and tightening the screws (28) to a torque of 8 Nm ± 10% (Sect. 3
- 3, Frame torque settings), starting with the front one.
Refit the silencer, as described in the paragraph "Refitting the silencer" of this section.
If removed, fit the copper washers (18) to the plugs (17), start the plugs into the vertical (22) and horizontal (24) head
exhaust manifolds and tighten them to the torque of 25 Nm ± 10% (Sect. 3 - 3, Frame torque settings).
If the silencer heat guard had been removed, check the presence of clips (43) on the silencer (4).