I replaced the stock NSK with a Nachi bearing with full Viton seals and high temp grease. I chose this because the Viton in the Nachi is a superior material at temperature and I wanted a higher temperature bearing. Choosing a fully sealed bearing was also important to keep the oil and grease separate. The caveat is I also modified my IMS shaft to eliminate the pressure differential in the IMS that will push oil through the bearing seals.