http://www.mintylamb.co.uk/suneedle/
A useful database to compare needles.
I used it to check the 3 sets off needles that I have acquired
AAA currently in use with the K&N filters
AAU currently in a pair of AUD616 carbs I am preparing to use (with the K&N filters and AAA needles)
ACD in a spare set of FZX1229 carbs
The results are in the chart above.
The AAA is the richer of the 3 needles
Found this info as well:-
Below is another chart I have found that compares popular needles and how they perform under different engine loads.
MGB tips mods and maintenance 