My 2008 Chevrolet Express 1500 is indicating Engine Power Reduced and Service TPS System, can a faulty tps system and or a really bad catalytic converter be the culprit?

I should have replace it at least a year ago, the catalytic converter has been bad, can it or the service tps system, or needing an oil change bad, (oil shows 0 %  for being effective and I know that I am not using the correct term for oil life), be the cause for my 2008 Chevrolet Express going into Engine Power Reduced mode? Also, when I am on the highway and I have gotten past an incline I can get it up to about 50 mph, but once I slow down or stop it has really low power taking off and won't pull any hill or slight incline. When it is idling, it is running and sounding like a tractor, vibrating and engine seems to rattle the whole front end. If I give it a little gas, it quite down a little and doesn't vibrate as much. I was told by someone that one of the sensors in the Catalytic Converter, or in the emission system has to do with the throttle, (throttle position sensor?), and because it is bad, the system doesn't know how much gas to give or how fast the car may be going because of not knowing how much the throttle is open then the engine power is reduced as a safety.