Definitelyloctite the power valves, it could cost you an engine.
POWER VALVES
http://www.nissanpathfinders.net/forum/topic/17104-threadlocker-on-power-valve-screws-pics/?do=embed
Please forgive my ignorance but can you explain the advantage of the 5150s &/or 5125s over the 5100s? They appear to no longer make the 5150s but I think it has been replaced by the 5160s. Thanks!