https://www.unseen64.net/saintsrowundercover/
Now you may be asking "And? Why are you telling us about this?" Well. The game for some reason isn't compatible with the actual PSP. Volition reps recommended using an emulator like PPSSPP but I wanted to play it on the true software but for some reason, the game gives an error when you run it! I had no idea where else to go for an active PSP community and I thought I'd come here and look for someone who could perhaps help other fans (such as myself) revive this hidden piece. Anything would be HIGHLY appreciated. Thanks guys!!
EDIT: 6.61 PRO-C and 6.20 PRO-B2 are the only tested CFW that I've heard that haven't been able to run it.