The ornamental design for an exhaustpipe, as shown and described.
FIG. 1 is a perspective view of an exhaust pipe showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a top plan view thereof, the inner structure at the ends of the pipes depicted by means of broken lines forming no part of the claimed design;
FIG. 5 is a bottom plan view thereof, the inner structure at the ends of the pipes depicted by means of broken lines forming no part of the claimed design;
FIG. 6 is a left side elevational view thereof; and,