The standard Holley needle and seat will hold back 8-9 lbs. of pressure. They do have a high pressure version that is good to 11 psi.
I try not to run more than 6 1/2 -7 psi even though I do use the high pressure needle ans seat. I use the new titanium model.
This feeds 2 Dominators and just under 1000 HP just fine.
[This message has been edited by Racing Ray (edited April 04, 2002).]