[webb452]

I would agree with earlier post suggesting the fuel pump or gas filter could be your problem. But seeing how your issue is with a Weber carburetor at higher speeds I might suggest checking the accelerator pump on the Weber. It is a diaphragm that can dry out and get hard and crack. It is found on the near the fuel connection to the carburetor and is connected with four screws. The carburetor normally used on Model A's is the Weber 32/36. I would suggest you purchase a new one before disassembly. The are not very expensive and can be found at most auto parts stores.