Draw-through carb info?

Those two threads don't say much about the carbs other than:
1. No changes are needed
2. Minimal changes are needed

I see that Holley and QFT have designated "draw-through" carbs (up to 950cfm). There must be a difference... or is that just a "marketing trick"?
Problem is that with those I'm still limited to about 15psi and I need to go past that to reach 1000-1100HP.