[700rpm]

You left out very important info in your initial post. It is hard to give relevant advice when we don't have all the facts and don't know what your setup is. As George says, two carbs changes everything, and two Tillies complicates the problem even further. But I'll take some blame for assuming we were dealing with a stock system. Messing with Henry's engineering always runs the risk of problems, especially before you are familiar with how the car runs stock. Take the dual carbs off and install your stock manifolds and Zenith.