If he bought the carbs New, I’m going to assume the kill bleeds have not been modified. When I raced my car, I had a fuel pressure guage that I could watch as I went down the track. If the fuel pressure dropped, it would start to slow down. The last six pack I built and tuned had a Carter that would make about 6 lbs. it worked great. Do you have the same fuel pump on the 440 as the 383? I started out with the black springs and they did not open much at all. Have you tried quicker springs? I’m a believer in a wide band O2 sensor to tune with. It really helps on a six pack.