Misfiring after installing new carburetor.

[E.D.75GMC]

Today I received my "new" Quadrajet from National Carburetors. Installation went without a hitch and it idled just fine afterwards.
Then I decided to take a drive around the block.
I had to give it a bit of hard throttle as I live at the top of a rather steep hill and as soon as I let off the gas it started to misfire. I checked for leaks, there were none. Checked the fuel filter, it was clean. Let the truck sit for a couple hours incase it was just flooded and went to start it up and still misfiring. All the hoses to the carb are okay. Plugs and wires all seem okay too. Really not sure what to check next, hopefully someone can provide insight.

I recorded a short video of it running but it won't allow me to upload it (something about a security token)