A method for manufacturing pellets from polymer, comprising: (1) melting polymer flakes in a first section of a melt processing unit to create a first single stream of polymer melt; (2) separating the first single stream of polymer melt into multiple streams of polymer melt by means of a separation element; (3) passing the multiple streams through a multiple stream section of said melt processing unit and exposing the multiple streams to a pressure within the multiple stream section of the melt processing unit as the multiple streams pass through the multiple stream section; (4) recombining the multiple streams into at least one combined stream of polymer melt; and (5) cooling the polymer melt and forming said pellets from the at least one combined stream. The intrinsic viscosity of the at least one combined stream may be determined and, in response, the chamber pressure within the multiple stream section adjusted.