How much input do you think Yella actually had on Niggaz4life?  I see his name in the linear notes for several tracks, but everything has a strictly "Dre" feel to it.  Don't get me wrong, I think Yella's production is tight....The only track that sounds like Yella production is track#9 (Real niggaz).  Sounds similiar to 2Two face featuring Leicy Loc off of his solo album.

i was thinkin this 2 but then theres this on the Menajahtwa CD they use the beat 4 "Dayz Of Wayback" and it says produced by Yella so i was thinkin its produced by Yella

Oh yeah?  I'll have to give that CD another listen.  I've never noticed that before.