Back to the original topic, I replaced my D3 tail light bulbs with LED's
See Here:
http://www.aulro.com/afvb/d3-d4-rrs/...ml#post1640875
I've since updated my rear lights to D4 ones and fitted the same LED reverse bulbs.
The difference is quite staggering, they have got to be 3 or 4 times brighter than the standard filament bulbs.
No issues at all fitting them.

