It sounds like the slides in the carbs are not going up. Remove the top of each carb, one at a time, and see if the slides are moving freely. Loose or bad connections between the air box and the carbs can do this, the clamps need to be tight and no leaks. If there are missing screws on the carb body on top, or if they are loose the slides won't lift. Also the diaphragms should be seated properly, they only go in one way and there is a tab that orients them.
Above about 5000 rpm the slides lift up needles that allow more fuel into the engine. If that does not happen, or if 1 (or2) carbs don't lift the needles the engine is not going to produce power and will hit the wall. It will seem like a fuel delivery problem when it really is a internal carb problem.
I speak for many when I say we wish we were there to help diagnose this, it is probably something simple and easy to fix. Don't throw the baby out with the bathwater, you'll laugh about it later.
Above about 5000 rpm the slides lift up needles that allow more fuel into the engine. If that does not happen, or if 1 (or2) carbs don't lift the needles the engine is not going to produce power and will hit the wall. It will seem like a fuel delivery problem when it really is a internal carb problem.
I speak for many when I say we wish we were there to help diagnose this, it is probably something simple and easy to fix. Don't throw the baby out with the bathwater, you'll laugh about it later.