I got my weber tuned fairly well, I have the round port intake so maybe that's why my low end torque is not too bad. I am also getting about 30 MPG at 80+ mph, with an egt of 1350, so I'd say i'm tuned good at WOT, I'm too rich at idle, but am waiting on jets.

I have a mild cam on my A15 and 2" cat back overall It's running good.

try #60 primary idle, #80 secondary idle, and fuel jets and air correctors similar to what was mentioned for the A12, or spend some $$ and have the carb shop tune it.