I sat down and watched the little how to CD that comes with the Edelbrock and the demonstrator states 7psi max on fuel pressure for the AFB style carbs. I'm running a little over 6. I initially suspected a possible over pressure conditon but around 6 shouldn't push those seats off. I popped the top on the 600 and found the float adjustments to be off per the video. I reset those and really improved idle on it.