What this does:
Stops traffic from spawning with tuner parts, apart from rims and suspension. Basically removing parts that would cause abnormalities with replaced cars.

Reason?
Many community made car models don't include their own tuner parts, such as spoilers and skirts etc. Because of this the game will use the original parts for the car you replaced.
Sometimes these cars have missing or misplaced bones, so the default tuner parts won't attach correctly.
At best the parts will appear on the wrong part of the car. At worst it will cause a memory leak, artifacts and eventually a crash.


Installation:

Use OpenIV to locate and open

..\Grand Theft Auto V\MODS\update\update.rpf\common\data\ai

and replace vehiclemodelsets.meta with the one included

Feel free to distribute this mod, use it in your own mods, make additions etc.

Thanks to ChOcOsKiZo @ gtaforums for telling me which file to edit.