The Audi R8 is one of my favourite cars and it looks great in red! Nice and subtle changes. Some things stick out to me:

The front rim is blurry, just a quick use of the sharpen tool or filter would easily fix it.
There's a green reflection on your front bumper which makes it look like there's grass nearby but the background clearly shows us that there's no such thing.
When adding a paint job like this It's very important that you redo shadows. An example is the side intake which is way too bright, just select the reflection of the vent and make it darker.