91 200q low oil pressure

[RRFS32D@PRODIGY.COM (MR JERRY BEER)]

  Finally got around to installing second oil cooler per Eric F.'s 
suggestion.  Car seems to run a little cooler in normal street 
driving, as it appears the thermostats on both open at relatively the 
same temp.  However, at speed,  when warm, oil pressure is down.  Now 
about 3.25 bar as opposed to 4 bar per guage.  Pegs guage at 5 when 
cold and idle is almost the same (difference is the width of the 
needle), just under 2 bar.  Other than bigger or longer hoses, any 
explanation for pressure drop? (BTW, fresh Mobil 1 15-50 synth).  Any 
cause for concern? TIA
Regards,
Jerry
91 200 STEADIA3qw