After doing some research about how to improve brake performance on my Jeep, I learned that a TJ power brake booster has dual diaphragms, as opposed to a single diaphragm that my YJ came with. Going from a single to a dual increases the hydraulic brake pressure from 1,000 psi to around 1,600 psi.
The swap isn't too hard to do. The one major difference that needs to be addressed is the brake rod length. My YJ measures 7.5", while the TJ rod measures 5.5". I found a thread on a Jeep forum that described how to correct the rod length, and make it adjustable at the same time.