Fuel Leak? Please help!!

I bought my first bike a few months ago. I have a 1980 Kawasaki KZ750 and i have a fuel leak. The problem is it is leaking from under a black box that feeds into the 4 carbs. It is leaking out of the bottom of this "box". I dont know what the name of the box is. It is black with grooves on the sides and it is like hard plastic or rubber. I need to know if I should go through the carbs or is this "box" the problem. Also this seems to be causing it to idle real low. Any thoughts?

Is it the airbox where the air filter sits under the seat?

Hi , your carb float bowls have overflows which feed into your air box . Your leak is coming from there which means you will have to remove your carbs and check your float heights and possibly clean your float needle and seat . Had this happen to me on my kz750 ltd h2 , found my float needle sticking open ! .
Good luck.

i hope you dont have you petcock set on "PRI" if you do the leaking from the airbox will be the least of your worries