I can accept Carlo being involved in the Sonny-whacking (motive-revenge), but what always seemed a little off was the decision by Mike to make Carlo his "right-hand man" when they make the move to Vegas. Up to that time Carlo was on the fringe and now just because he grew up in Vegas, he becomes Mike's assistant. - OR - had Mike made up his mind at this time that Carlo was guilty and this was a ploy to snag Carlo when he is unsuspecting.