Restoring 5.3 Untethered Jailbroken ATV2

I’d like to restore an ATV2. It is currently on 5.3 and has the untethered jailbreak. I’d like to restore it to 5.3 and re-jailbreak it because it is having sugglish performance. How would I go about restoring to 5.3 without updating to the newer versions? Thanks for your help.