I did a modification to my stock WR muffler that worked well with WR or YZ valve timing. Here's what I did for a cost of $5.00: 1. Buy an automotive 1 3/4"-90 degree exhaust bend. The size is important; it fits perfectly over a sleeve inside the end cap. 2. With the muffler and end cap on the bike, slip the female end into the muffler end cap until it stops, angling the bend down. 3. Through the original insert screw hole in the end cap, drill a small hole into the extension Install a short self tapping sheet metal screw. 4. Using a hacksaw, cut off the new extension to suit your preference of down angle. Cut square to the pipe centerline at the cutting plane. Debur the cut with a file and emery paper. My turndown extended about 3" from the end cap. 5. Seal the extension outer diameter to the muffler cap with black silicone. 6. Raddle-can paint the extension and sealer black. Not required to be heat rated. This install looked good and did the following for my bike: A. Provided water protection to the upturned stock cap opening. B. Significantly lowered the sound level at low throttle. C. Preserved all the power characteristics of the open WR end cap. This is true for all the "dial in" combinations discussed in this forum. D. Leaves the spark arrester screen in place.