a few ive bought have came with out the tanks ive always just stuck one on. it runs fine with out but its a risk at the end of the day am not prepared to take with a good few thousand at risk if any thing happened. hell you technically dont need that tank ontop of the brake cylinder you could just remove that with a small bit of pipe. it will run perfectly fine right up untill that one day it totaly fucks up and probaly kills you just my though but if its a car you take pride in id either run or have a nice custom one made up.