Debated with myself over a repair's part origin last Friday
Had to fix an old film camera's advance lever. Went with a generic part to cut costs, but now I'm second-guessing if honesty matters more. The thing functions perfectly, which almost makes it harder.
Guilt sticks around because you know the story behind the part. It works, like young.kim said, but you're always aware it wasn't exactly above board. That knowledge just sits in the back of your mind every time you use the thing.