Captain reported that an engine malfunction in flight resulted in a partial loss of power in one of the engines. The flight continued to planned destination and made a safe landing.

Narrative

Shortly after departure the left engine manifold pressure gauge began to decrease at a rate of 1 inch per 5 seconds; I began to execute the engine failure in cruise flow. However; upon reaching the 11th item on the memory items; I elected to not shut down the engine as the engine had stabilized at 20 inches of manifold pressure. With reasonable certainty it was concluded that the left engine had suffered a turbocharger failure and was now producing partial power. This partial power condition was verified by a slight yawing of the aircraft that was corrected by rudder trim. Once I had reached the cruising altitude of 8000 ft. MSL I weighed the option to return to ZZZ2 or to continue to ZZZ1 or to divert to ZZZ3. The decision to continue to ZZZ1 was made based on current RCAM (Runway Condition Assessment Matrix) values; fuel on board; ETE (Estimated Time Enroute) and emergency services available.At this point a [priority handling] call was broadcasted to ZZZ Center and [priority handling was requested]. Sitting in the co-pilot seat was a pilot who had worked for Company and served in the capacity as an [aircraft type] Captain; ironically this former captain also had time in Aircraft X. I made him aware of the situation and requested he assist me in reading a checklist from the QRH. I also requested that if the engine failed; to take over the radios while I flew the aircraft. We discussed the situation and discussed alternate options and we both agreed that ZZZ1 was the best choice for the situation we were in. From that point the flight continued to ZZZ1 where after being handed off to ZZZ1 Approach; they informed me the runway was going to be closed for the [priority handling]. I elected to come in slightly high and planned to cross the threshold at 100 kt. to allow for any abnormal handling characteristics. After clearing the runway at Taxiway XX; I was confident that the aircraft could be taxied under its own power to the terminal. This was determined due to the lack of 'white smoke; and no trace of leaking oil.' I also cancelled the [priority handling] at that time. The passengers were not notified of the [priority handling] and no comment was made questioning why a fire truck followed us to the gate. The decision to not notify the passengers was made when [priority handling was requested] during the flight. Due to the relatively normal handling of the aircraft; occasionally I looked back and it should be noted that all the passengers were asleep during the majority of the event. The former Company Captain informed me that during the walk into the terminal from the plane no one made mention of the fire truck; only that it got a little bumpy" during the decent. The aircraft was written up. The event concluded there without further incident. Based off of the engine indications it appeared that the waste gate had failed."