Kirby-Morgan has discovered an inconsistency with some of their  regulator assemblies P/N 505-069 that were manufactured between January 1, 2005 to March 1, 2005. The tube that holds the inlet valve and lever arm on some of these units in this batch are misaligned and consequently the lever arm sits offset. This offset if large enough will not allow the lever to travel smoothly and may increase the inhalation effort. Regulators that have this configuration should be taken out of service and not used until they have been replaced.