I have heard that switching the bulbs around in the socket helps with other issues might be worth a try.
Tried that nogo.
Have you measured the voltage at the light connectors? I have no idea how sensitive your LEDs are to very low voltages but you might want to check that out so you can rule out any inductive coupling from adjacent wires in the loom. Like Daryl said, a resistor might be needed.
My gut says that this is a grounding issue. Whenever I get weird electrical stuff happening, that is usually the cause but LEDs are special.
These same LEDs worked great in my 2006 as well as two other bikes. The voltages stated in my first post were measured at the
tail light harness connector with the bulb plugged into it bypassing the bulb adapter.
The ground issue was my thought too. That is why I connected a good ground to each bulb. My technical background tells me it
is a bad component in the signalling circuit.
Although the resistor solution may solve the problem my OCD wont allow me to do that.
This may just have to be added to my winter project list.