The cornerstone of my back training for 20 years has been pull-ups. Some workouts getting into the low hundreds for reps. I believed Arnold that they were the way to create your "wings". Over the last few months, though, I have de-emphasized pull-ups for row variations: barbell Yates rows, db rows and chest-supported rows with pull-ups as secondary, usually only 50 or so pull-ups on an average back workout.
I have had a noticeable positive change in back width, which seems somewhat counter-intuitive. I always thought (thanks Arnold) that rows built back density and thickness, not width.
Probably also a good lesson for just being willing to experiment and to go out of a comfort zone. I had become sort of a pull-up specialist.