Fuel delivery issue probably
You are out of hand brother. One minor detail, your carb bowls will run out of fuel unless you buy wedge shaped floats. These carbs are not meant to take G forces east and west and control fuel level, just north and south. Might even throw a cup full of fuel at you too out the vents when you accelerate forward. Food for thought, maybe when it runs out of fuel, the hesitation will be timed about the same time you realize you are on your death run, who knows. If we don't hear back from you after testing, I'll have a clue what might have happened to the driver.
Good luck
Bruce