LED rear lights problem

[PetrolDave]

The canbus ones just have a value of resistor already built in (but normally too small for Audis) so this means you will more than likely need a smaller resistor to get it to work than if using non-canbus LEDs.

If the LEDs have a parallel resistor already built in then you need to add a resistor that has a smaller power rating, but draws less current - so it needs to be a LARGER resistance value (since for a given voltage current is inversely proportional to resistance).