Is there anyway to do this?  So that when I click on the source button on my steering wheel I dont having to cycle through these?

Great question. I don't think so, but I would like to add it to my future feature requests.

I don't think you can remove, but you can move them around and put them in whatever order you want.

I just got a car with a Pioneer AVIC8100NEX and want to remove Pandora and Aha and other sources. I'm surprised that I can't do it. I was able to customize the source list on the JVC KW-NT3HDT on my other car, and that model must be 7-9 years old.