If your cats are gone, you change your oil once a week, and you don't drive it for more than 15 minutes at a time, you'll be fine. Otherwise, DON'T DO IT.
Why would you want to anyway? Are you experiencing an overly lean condition? Hell, if you just want to waste more gas, clog up cats, and dilute your oil, install a set of old O2 sensors. As they go bad, they read lean, and the ECM tries to correct it by adding fuel.
I personally wouldn't do either, but if you feel compelled...
