After replacing the exhaust, I am getting message reduced power and keeps shutting off?

Hello, how much of the exhaust pipe came off, how far back? There is a rear oxygen sensor after the first thicker section of the exhaust, the Catalytic Converter. I'll post a picture of that, but there is also the Evap system back near the gas tank that is responsible for fuel vapors being drawn out of the gas tank. And the evap system has components with electrical wiring running to it. If the broken off exhaust section got hung up and melted any of the evap wiring it can cause all kinds of things to happen. If you can the best thing to do is get the vehicle to an auto parts store so they can scan the engine computer for any diagnostic trouble codes that would have been set if there are potentially melted wires.
I assume the check engine light is on as well.
In yellow is the rear Oxygen sensor and in green is the Catalytic Converter
The second diagram is your gas tank looking at it from above, everything in yellow has wiring and electrical connectors going to them. So, the fuel pump wiring is on the very top of the tank and Evap Canister is the square looking box with vapor lines and electrical connectors on it.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing