Running warmer temp after exhaust mods.

underhood temps sometimes rise with headers. Nothing to worry about. As l0ong as it ain't running hot nothing to worry about

The engine could be running slightly leaner (and warmer) because the headers/h-pipe are allowing more air to flow through the engine. Disconnect the battery for 10 minutes to allow the engine computer to reset itself. After a few miles it'll adapt to the freer-flowing exhaust so the engine will run as cool as it did before and make more power.