i have a 350 with a lunati cam with .457 lift and a 600 holley vaccum secondary carb on it. My problem is that at idle it runs overly rich at idle and sounds like it has no power and loads up at a stoplight. But as 60 or 70 mph. it runs like a scolded dogand better than any other car. When I drive it hard or for an hour at long distances at finally stop the idle speed seems like it is too high and sounds like its running away. But when I drive for about 20 minutes when I stop the car sounds mean and idles fine until it starts to load up. When I floor it off idle it bogs and falls flat on its face. COuld I just lean it out at idle with the mixture screw or could it be a blown power valve butI just repalced it not too long ago. Please I need some help so I can enjoy my car.