The ornamental design for a diffusercover, as shown and described.
FIG. 1 is a top perspective view of a diffuser cover;
FIG. 2 is a bottom perspective view of the diffuser cover;
FIG. 3 is a front view of the diffuser cover;
FIG. 4 is a rear view of the diffuser cover;
FIG. 5 is a side view of the diffuser cover;
FIG. 6 is another side view of the diffuser cover;
FIG. 7 is a top view of the diffuser cover; and,
FIG. 8 is a bottom view of the diffuser cover.
The shade lines in the Figures show contour and not surface ornamentation. The dash type broken lines in the Figures are for the purpose of illustrating unclaimed portions of the diffuser cover and form no part of the claimed design.