I was going to add an LED strip light in the trunk and 'tap' into the existing trunk light for power ..... however, upon looking at the OEM trunk light housing I noticed a diode or something similar in the OEM light housing ..... Can I tap before or after the diode for my additional lights? or is there another method ....

 

I tapped into the existing trunk light to add 2 LED lights on the underside of the trunk. This lights the whole trunk when the trunk is open.

 

I would meter it to see if there's any voltage difference on both sides of the resistor. It may just be a diode to prevent feedback on the wire.

 

You can tap off of it. It will be fine.

All the LED's and fluorescents in this picture lighting up the my trunk are tapped off that circuit. Just remove the stock bulb. You'll be fine. I had 8 LED's and 12 fluorescents.