Nothing to worry about.
Nothing to worry about. Cylinder deactivation works fine today. It was actually Cadillac's bright idea. Designed to improve gas mileage and reduce smog. But the electronics of 30 years ago were not up to the task of reliably working correctly. To put their 368 V8-6-4 engine into perspective, they were able to only get 140HP out of that 6.0 liter V8! In modern engines with modern electronics it's not a problem.