E85 control units with lambda probe measurement for mixing detection

Hello, how is this supposed to work if various manufacturers of E85 control units claim that they can disgnose the mixture by means of Lambdasone? At my W124 500E, for example, I only have an older narrowband probe, as most vehicles, to my knowledge, still have today. Is the Humbug or funzt dat? – Best control unit for my V8 ??? 🙂