Some people use air seal on all the fittings, and boot. I'm not sure what the boot is designed to do, either to keep dirt out or keep air from leaking. Other things you could do is replace the orings on the needles, might need to buy new needles to do that.
I ended up using teflon tape around the carb fittings, and even wrapped teflon tape around o rings above the needle threads. You can check this by blowing on the carb and air leaks should be minimal. You'll have to put your finger over the exhaust to do this, but it shows you where air is leaking.
Detroit Radio Control Car Club