carb ported and manifold vacuum question

Are you sure your correct on what port is ported and what one is manifold? It sounds to me like you have them switched because the manifold vacuum should be the higher of the 2. There's no possible way anything in a carb can amplify vacuum. Like 73 Dart pointed out you really shouldn't have any vacuum on the ported port at idle. I ran a 625 Carter on a 360 with a very similar build as yours with no idle problems or vacuum port problems. Also ran a 750 Holley on it and it might have made 10 more hp at the very top end but the smaller carb was more responsive. I'm with 73Dart in definitely not going smaller though.