My USE4 wobbles on decel.
I honestly think some of it is from the tires flat spotting when sitting on the side stand. Try turning the handlebars full lock right when you park, seems to help on mine.
I know that every HD dealer loves to pump that steering head so full of grease you will spend all summer cleaning your left fork. I don't want to pump it full of grease, but I have read others here saying it is a need to do item in order to get grease to the upper and lower bearings of the steering neck. I have not put more than 4 squirts in mine yet. I read some guys saying it takes nearly an entire cartridge.
I will let you go first...if it fixes the wobble I guess I will spend the rest of the summer cleaning my left fork from the grease that melts out and down while on the sidestand.

I am searching for opinions on the need to see grease ooozzing out the bottom of the steering head.....
I am thinking those who said "loose steering head bearings" are the first place to look.