Indeed, there are lots of plugins that emulate pretty accurately tape saturation. Yet, there is something they do not quite reach.. If you listen stuff old SJ, Whitehouse, Ramleh, Consumer Electronics etc besides tape, there is often room/space/amplifier etc and digitally adding some "room echo" barely is the same thing. It may sound good, but barely same thing. My advice would be to aim to generate situation where noise happens in a way it should be, rather than spending time searching how to make virtual substitute for it.