hello, we are having the same issue. do you have a picture you can share of the extension? Thanks
we thought we had fixed the problem. Put the stock windshield back on, took the trailer out a couple times for day trips and had no issues. Then last sept we took our usual 18 day ride which includes the Norcal rally in California, and as soon as we left, we exhaust problem was back.
The theory now is that when we did the day rides, the trailer was empty, and once full ( or nearly) the bike is working just that much harder, so the exhaust output is more.
Unfortunatly, after the sept trip, our riding season is over up her in the great white north, and the bike has been put to bed for a couple months already, and will be away until some time in april .
Once out of storage, my first plan is to cut off the 2 pipes that are the final exhaust, and rotate them so they are pointing outwards. I will load the trailer up and take for a spin to see if this improves the issue. If it doesn't, I will fabricate up two that are longer, and gets the exhaust further out into the airstream.
Sorry I couldn't help more. but winter is here, and I don't have a garage.
If you find a solution, please post it here.
Ray