Edelbrock mid throttle problem

Hi!

I have a tuned 440 magnum and I have edelbrock 750 performer carburator.
My problem is that I can´t get it running well at mid throttle, so it is lacking power. I have been working with jets and testing , also been adjusting ignition advance multiple times. It works really nice but the power stays only at high rpm. Engine doesn´t bog or stall, it just misses power.

Many have said to me, that you have to change the carburator.. What do you think?
I have been adviced to buy quickfuel 850, with annual nozzle body

440 magnum
906 ported heads
10:4 compression
Compcams XE275HL-10 (in. 231, ex. 237)
727 with 1800 stall converter
Headers and 3" exhaust
(Power should be around 400hp)