As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER DEPARTURE, A MINOR FLUCTUATION OF MANIFOLD PRESSURE WAS OBSERVED ON THE RT ENGINE. THE ACFT RETURNED TO DEPARTURE WITHOUT INCIDENT. UPON INSPECTION IT WAS DISCOVERED THAT THE RT ENGINE TURBOCHARGER CENTER BEARING HAD EXCESSIVE WEAR CAUSING THE TURBINE/COMPRESSOR WHEELS TO DRAG CAUSING THE FLUCTUATION OF MANIFOLD PRESSURE.