Your Weber is a good carb and just needs setting up. Your Primary idle jet should be a .55 as a starting point, you can check it in 2 mins. Here is a link for tuning it. http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm your fuel pressure should not be over 2.5 to 3 psi. I would start by pulling the spark plugs and looking at the color, should be light brown. white is lean, black is rich.
Also check your timing with the vacuum advance hooked up, at high RPMs some Weber 32/36 vacuum port will hold vacuum all the way to top end without backing off.(meaning mechanical and vacuum are both advanced at the same time at top end) If this is happening your total end timing will be way to high (should not be over 34) you can burn a piston. I have been run a Weber on my A14 for 30 years and it has been great. Here is a list if the jets in my A14 (should be a good starting place)
Primary main jet 140
Secondary main jet 135
Primary air corrector jet 165
Secondary air corrector jet 160
Primary idle jet .55
Secondary idle jet 50
Primary emulsion tube F50
Secondary emulsion tube F6