I did this exciting mod to my XJ-6 back in 2004.
After upgrading my car to blinking / flashing sidelights,
I would not go back to the stock, static sidelights.
Europe and Australia XJ have FRONT flashing sidelights,
but the US and Canada do not.
This mod makes both Front and Rear sidelights flash
with Turn Signals or Emergency Flashers,
AND they continue to work as normally.
I made a video of the two ways this mod works,
and wrote detailed instructions on how to do it,
for those who want their sidelights to:
1) flash / blink with the Turn Signals,
2) flash / blink with the Emergency Flashers,
3) and continue to work normally as sidelights.
with a simple one-wire mod to each sidelight.