Welcome to CF.Cool but what did you do to fix it? As for me 09' CTS 6cyl di . I replaced the ignition coil on cylinder 2. Purrs like a kitten now. It is amazing how bad the engine runs when you drop a cylinder. Don't forget to polish that Cadillac symbol on the front of the grill.
We could do a necro-mode 6 test...hopefully showed up 8 years ago...
Bill