Will opening up the ends of stock 103 baffles cause vibrations felt by the passenger. I'm trying to locate the source which she says is most noticeable at 55mph. It's a 13 Eglide Ultra with 8,000 miles.

 

Anything is possible. Could be that now at that speed and particular rpm the muffler starts to resonate which could in turn cause a vibration.

 

try to isolate whether the vibes are road speed or motor speed related.

if you are running 55 mph in 6th gear, that is the bottom end of the motor wanting to fall out on the pavement, 2100 rpms is too low a motor speed for that load.

you can isolate by hitting 55 mph and pulling in the clutch and dropping revs (or reving higher)..any change?

you can try a different gear

or you can find the rpm range that bothers her, and try that same range in different gears

make sure that the exhaust is not contacting the frame at any point

mike

 

Your bike will happily run at 55mph in 4th, 5th and 6th gears, so do as Mike suggests and see if changing gear changes what happens. Report back!