I HAVE A 400 SMALL BLOCK BORED 40 OVER,.470 LIFT 224 DURATION COM. MAGNUM CAM ,350 RODS, VORTEC HEADS,EDELBROCK RPM PERFORMER INTAKE AND A 670 CFM HOLLEY STREET AVENGER CARB. The motor has good power but it has a hesitation when you hit the gas hard. I thought it might be getting to much fuel at one time when the secondaries opened, I changed the spring to delay the secondaries, it helped a little but its still there. The timing is set at 12 degrees at idle. It has a vacuum advanced hei, I tried connecting to manifold vacuum. What else can I try.