Your biggest problem in removing the ac will be finding something to take the place of the ac pump. Your serpentine belt is going to have a place to go. I'm sure if you look hard enough you'll find a kit for doing this. As far as power gains I don't think your going to see the difference all that much. Going from power to manual windows is not usually done and there were no C4's I know of that had manual windows that you could use for parts.