Fuel supply problem?

Alright so I called the holley tech line to tell them about my problem. I have a 750 dp carb on a 400hp 340 that turns 6500. Nothing special but the car has a bad part throttle miss like it's running lean. He asked me the jet sizes. I've went from 71 80 to 80 87 with hardly no change in performance and car still has the miss. The fuel system is plain and simple. Factory tank steel line to a mechanical carter high flow fuel pump to carb. I'm thinkin about running a different carb to see if there is a difference. I believe I've mentioned this before on here but I've got a little different info now but sorry for being repetitive lol I'm just annoyed with this problem. Other then this the car runs darn good down the track.