What was found
TAXIED FROM THE RAMP INTO THE RUN UP AREA, DID RUN UPS AS NORMAL NOTHING ABNORMAL DETECTED. TOOK OFF 16L REACHED V1 AND ROTATED AS I NOTICED THE PLANE WAS A LITTLE SLUGGISH TO LEAVE THE GROUND AS I GOT AIRBORNE I NOTICED THE TORQUE FOR THE LEFT ENGINE STARTING TO CLIMB I TRIED TO PULL IT BACK BUT IT CONTINUED TO CLIMB. I THEN SECURED THE ENGINE AS THE TORQUE WAS GOING PAST 4500 AND NOTICED I WAS HAVING A HARD TIME MAINTAINING ALTITUDE. I NOTICED THE PROBLEM HADN’T FEATHERED SO I FEATHERED IT AND GOT MY PERFORMANCE BACK. I DECLARED AN EMERGENCY AND TURNED LEFT FOR A DOWNWIND TO RETURN TO 16L. AS I TURNED BASE I NOTICED IT WOULD BE SAFER AND EASIER TO LAND 16R SO I SWITCHED TO 16R AND LANDED NO FLAPS WITHOUT ISSUE. I EXITED A5 AND SHUTDOWN THE PLANE AND WAITED FOR THE TUG TO TAKE ME BACK TO THE RAMP.