Interesting. I will investigate this as well and see if I can incorporate this all together.
Thanks everyone

So, quick update. I reconfigured the inside of the new lights to reflect the wiring schematic in the old lights. Wasn't hard to do, just took some time. I only did one light to see if there was a difference but it didn't change anything. Both of the lenses work as needed but the dash is throwing me the lights telling me they don't like what's going on back there. My next thought is to try the old bulbs to see if that makes a difference.
I had to rebuild the rear end so this hasn't been much of a priority since they do work.

AdamE53, there is a MUCH faster and simplier fix for your common problem.
you actually buy Mercedes Bens light socket to fix the problem with your original lights. So basically you bought facelifted tail lights, for no purpose :(

read this
https://xoutpost.com/bmw-sav-forums/...t-fix-diy.html

I like your idea and would definitely give it a go. However, the wife and I prefer the look of the newer lenses over the old amber ones. They do work exactly as they should which is good enough. The lights on the dash are temporary, I'm sure I'll solve that when I get back around to it. Thanks for the link though.

So another update if anyone is interested.
I finally finished rebuilding the rear end and was able to come back and revisit this issue. I had a closer look at the pre LCI lenses again and took a closer look at the bulbs and bulb holders. I noticed that the LCI lenses have four brake lights, all the same bulb. Pre LCI lenses have similar bulbs on the bottom and different bulbs for the middle, as well as a different holder(reen). I used a power source and tested everything to make sure I was clear on the differences between both. I'm sure a lot of you already know these differences but I will recap my findings anyways :thumbup:
My car didn't like the new lenses because of what someone mentioned earlier in the thread about different bulbs. My car was looking for that different bulb when braking and was throwing faults when it didn't find it. I basically had to modify the middle sockets of the LCI lenses so that it would take the green bulb holder and dual filament bulb, instead of the white bulb holder and single filament bulb, for normal braking and heavy braking lights.
I've only modified one lens so far but the corresponding dash light for that side is now gone and the car is happy. Light functions as it should and looks much better than the amber pre LCI lens. Took a bit of work to figure out but I am happy with the results.

Good news!

Thanks for the info in this thread! I'm actually an amber fan, so I bought a used set for my '05 E53... All kinds of brake warnings in the cluster, even after verifying the bulb connections (which were/are in fact quite sketchy!).... Didn't realize the facelift cars have PWM controlled brake-lights and different pin assignments... I can get a set of Euro facelift ambers, but for some reason the left side is $65 and the right side is $236 at ECS... Just my luck!