So far I havent had a problem with my stock 3 needle composite carb, its very responsive to tuning and I can run the engine with awsome performance between 200 and 210F. I think I might have a leaky front bearing though After I fill the engine up with after run oil and come back the next day theres a small puddle of ARO under the car. This could be because I nearly flood the engine with ARO though, I rusted a crank once so Im not taking any chances with this engine.
I distribute Sirio in my country and from what I know, the earlier batches of .12 engines had a loose low-end carb slide-side needle. This caused the needle to turn too easily and caused some air leaks. Remedy for this problem was to put a little (and I stress only a little ) loctite 242 on the thread of this needle and put it back in. You will have then a bit tight turning needle but now without leaks.
Another problem we encountered was with the carb retaining pin. The pin diameter are just too small and caused air leaks too. After running you will notice oil/dirt collecting at the pin's ends. To cure this, just coat the pin and hole with very little amount of silicone gasket maker and wipe off the excess before installing back the carb on the crankcase. This way you will be able to have a good and stable idling engine.
Good news is that Sirio has corrected the low-end needle problem and have also added a second o-ring inside the crankcase below the retaining pin level.