oil pump

[180sx]

how can you tell if oil pump is gone to a better place.??? i've previosly mensioned that when my mechanical timing was reset the oil pump/distributor gear that sits on the crank was put in backwards(figured when took it appart) but car run for about 2 weeks than stalled and will not start. i just finished getting new distributor spindle and oil pump gear installed(the old ones had broken thread and teeth), when car started the engine is really loud(the valves and chain) the oil lapm is on(oil is right on the level) as well won't rev past 2500 rpm.So far i figured must be an oil pressure problem. some advise or pointers ill be really helpfull thanks.