I'd see what the psi is at the carb inlets at the end of the quarter (want several psi). Wouldn't want to leave it that way but for 1 quick test you could T at the carb inlet(s) & run a line in to a gauge in the dash & see what you have. Wouldn't pass tech but could do it on a deserted street . & if delivery is adequate & if still lean you might be able to tap the other side of the AFB air horn to make a dual feed inlet