I know exactly what you are talking about. I get a pump in every part of my body except my BACK!! I have tried everything. I have been doing 4 exercises 4 sets of 10+ reps.
1. behind the neck pull downs
2. barbell or dumbell rows (till I almost puke)
3. close grip pulldowns
4. T-bar rows or one arm cable rows (till I can taste what I ate that morning)

I am getting results! But I never leave with that pumped feeling?
If you find something let me know, I have done almost everything.