Second brand new Holley carb flooding?

A good needle and seat will hold up to 11 psi before it blows open from too much pressure. I had to go through several before I found a nicely matched set that lasts a long time. Three carbs = three times the headache when they aren't right. Check your fuel system for contamination, run several quality filters and make sure you have less than 6 psi MAX for street use.

I run 5.5 lbs on the street, but at significant volume. My new system took a while to get small bits of needle and seat disrupting contaminants out of it. Then I went through about 7 needle and seat sets until I found good ones. It's a process of elimination and persistence.