If you get that gauge in there with you when your WOT under load, you will see whats happening. It recovers when you drop a gear and ease up on the thottle because your carb get's back some much needed vacuum signal. I am pretty sure Edelbrock has springs available to change the tension on the "air door" for the secondaries, I think a stronger spring might help there. If you go bigger on the jet it probably will help pull the hill, but it may make the secondaries way too rich when you arent under a load. The air flow just needs to pull harder on the jet you already have. Basically you may need your secondaries to come in less or at least later. Just throwing some idea's out there.
