I do not recommend this, just telling you what I did.
Using my Dremel Tool and cutting disk, I removed the "downturn tube" as close to the exit of the muffler as possible. This will take some patience and several cutting disk.
CAUTION!!!! WEAR SAFETY GOGGLES/GLASSES!!!!
Once this was done, make a trip to the local auto supply and purchase a chrome exhaust extension (slightly larger than the existing outlet, because of the "fold" at the tip).
Cut it to the desired length, and force it into the end until it is flush with the flat part of the muffler where you remove the "downtub", (use a rubber mallet to avoid screwing up your new chrome tip). This wil cover the outlet from the muffler and yes, for you "pickers of nits" there may be some slight leakage of exhaust around it, so what!
I then drilled and tapped the bottom of the existing outlet into the new extension, in two (2) places (about 30 degrees apart) to prevent it being ejected when everything heats up.
A test ride of over 100 miles shows no more soot build up on the muffler and the extension seems to actually make the exhaust note softer.