I do not think that the 1990 E-Class models had the "bio" wiring harnesses. I know for a fact that at least on the S-Class, it was OK up through the 1991 model year. You are right, it was seen on the "new" for '92 S-Class (W140), though some say the ones made in late 1991 didn't have it, but I wouldn't bet on it. My 1993 400SEL that was made in September of 1992 had the bio wiring harness, but thankfully has been changed.

I think that the E-Class was also ok at least up through 1991, but probably even 1992.