For those of you having trouble rooting your Sprint Galaxy S4 on latest MF9 firmware, there’s an easy way by using CF Root by XDA user ChainFire.
Step 1. First, you will need to install either CWM or TWRP recovery. Follow a or b below:
a. For installing CWM, follow steps 1 through 6 here.
b. For installing TWRP, follow steps 1 through 9 here.
Step 2. Download the latest CFRoot on your phone (or download on your computer and copy to your phone.)
Step 3. Using CWM or TWRP, find the CFRoot zip file and install it then reboot.
You should have a fully rooted Sprint Galaxy S4 on MF9 firmware.
Credits – ChainFire