Read in the tech section that the A12 carby has bigger jets than A14-15 carbies, thus it is beneficial to use an A12 carby on A14 or A15?

Wanting to access people opinion and experiences with this (if any)?

been using this setup...

as long as there is no major mod to your A15, should be no prob

But would it give greater performance than the standard carby?

If so, Im aware that the gain in performance is very small but Im just curious!

I doubt it would give you better performance. The carb bores are the same size. The jetting is still not optimum (it's not optimum for the A12 power, either). Be aware that some newer A12 carbs have smaller bores.

It should run OK on an A15, but the A15 air jets may be different, and so the A15 carb might actually run richer at full throttle. Who knows? Dyno your car before and after, and tell us how it goes

my primary jet is 137 while secondary 150

forgot the bore sizes