I have found that often the AI Image generator tends to crop off bits of the car which would otherwise be a great image.
I have found a new web site called 'Uncrop", which is also an AI type site that lets you add to images. The opposite of cropping an image. You highlight areas on an image to add to and it will work out what to add.
Here is an example of Uncrop in action if you look at the 1st image I uploaded on this thread and compare it to this one, the car is now complete.
You can keep regenerating 4 at a time until it gets it like you want.
I am guessing it works best with scenery and what not, so it will be hard to generate large areas of missing car parts. But for smaller areas it may help.
This one is not perfect but you can also see the difference when compared to the original on page 1.