94 Crown Vic. Oil Pressure issue?

Have a 94 crown vic 100 000km the oil gage has always sits at the R in normal .. it dropped recently to just above the M in normal. I recently had the alt. changed aswell.. I brought it in today they checked the alt the oil pump everything and can;t find anything changed the oil and it hasn't changed anything. I have run it over 1000k since i first noticed it and no issues . engine has been checked for codes and nothing .. lots of power no noticably knock .. ive been told not to worry but id rather not be stuck at the side of the road ... isn't oil pressure regulator either .. anyone have simillar issue can suggest something (lucas / tune up / faulty gage or sending unit) i'm really at a loss ...

thanks

CC

I would suspect that the strainer is plugging up you have to drop the pan to check this.
http://www.autopart.com/tools/toolsmain/tool/T_2001.htm
Use a manual gage and check the actual pressure before doing anything else.