Are these injectors seated properly?

Thanks for the image, this can be normal but to be sure there is no vacuum leak, which would be the only problem you can follow this guide when the engine is cold only to see if you get any change in engine speed or if it idles better.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If there is a difference the injectors will need to be removed and the O ring seals replaced. This guide can help with instructions below to help you on your truck:

https://www.2carpros.com/articles/how-to-replace-a-fuel-injector

Check out the images (below). Please let us know what happens.

Seems like there's a small gap compared to the other side.

Hard to tell as the image is a bit dark. Normally there is an O ring and the injector bore has 2 steps that it sets into. Those look like they may not be pushed all the way in, but if the engine is running okay, isn't leaking fuel and looks like it has been that way a while they are likely okay.