Last week I bought a new summit racing 600cfm carb to replace my 500cfm eddy. I had read great things on the annular boosters and I do feel the extra power. My problem is that I have always ran manifold vacuum but this carb doesnt like it for some reason. I have the mild isky cam. bored 0.60 292 with mummert intake and headers. Pertronix conversion in dizzy. original t98 trans. when I hook it up to manifold vacuum it wants to die when you blip the throttle quickly. It revs nice but then rpm drop super low. I have tuned with vacuum gauge as well. Now on to timing. with the eddy I had to retard the timing a bit to use manifold vacuum. have you guys had to do this? Whats you timing method when using manifold vacuum?