Why does my regal have no power?

What is your question?

It barely accelerates in manual and gets to 40mph. In auto it tries to shift from 3rd to 4th but when it does it kicks back to 3rd. Can anyone tell me why and what I need to do?

What makes this problem better or worse?

I changed the fuel pressure regulator and the fuel injector pressure sensor. I cleaned the throttle body the map sensor and the fuel pump. I changed the oil and spark plugs. The tapping sound stopped and its not stalling at stops but it's putting around now. It's not registering overheating but feels hot under hood now.

How long has your 2011 Buick Regal had this problem?

About a month. Was driving fine and picking up speed except for the stalling at stops.