Not sure whats entailed in the "kit"
To increase pressure on most kubotas is just shims under the relief spring. Usually thin washers like #10 machine washers work.
But dont do ANYTHING without a pressure gauge and knowing what your at currently, and what you will be at afterwords.
AS far as whether you "need" it or not.....probably not. The loader and 3PH is strong on that machine. I dont think there is an attachment made that you would use behind a 32PTO HP tractor that it wont lift. And the loader.....unless you have loaded tires and 1500# hanging off the 3PH......you aint gonna find the limits of what the loader will lift because the back of the tractor will raise in the air instead.