Shortly after liftoff, the pilot felt the aircraft yaw left and noticed that the left engine manifold pressure had dropped from 42" Hg to 29" Hg. He analysed a turbocharger failure and elected to keep the engine running in the normally aspirated mode. At approximately 400' the pilot saw smoke and fire coming from the right side of the engine. He secured and feathered the engine and made a single engine landing. Subsequent examination revealed the right side common exhaust pipe from the #1, 3 and 5 cylinders to the turbo had separated. This separation allowed hot exhaust gases to impinge on the engine compartment and burn through the cowl and several wires. It was determined that the detached part had been replaced 1.5 hours prior to the incident. Investigation revealed that a wrong replacement part was used which was shorter than the required part. Installation was possible due to overlapping exhaust tube slip joints. Poor organization and numbering of parts catalogs was cited by the maintenance facility as contributing to the installation error.