Yeah dude, back pumps suck. I just found this out on my first ever Trest run.
Those 19-nors tend to give you those crazy back pumps and since the deadlift will hit that entire posterior chain pretty hard, it's just going to accentuate that feeling.
Supplement with 4g of taurine. I've read of some guys doing 6, I stick with 4 myself. A shortage of electrolytes tends to be the cause as well. I take 1 hammer strength endorulyte pill before my workout and that seems to help considerably in combination with the taurine. Hammer strength is the brand, endurolytes is the product.