According to the 99 FSM, the minimum readings are 13 at 600 rpm, and 37 at 1600 and above. The pressure relief kicks in at 75.
My 99, with 163K miles, reads around 20 to 45 or 50 normally with 10-30 oil and a good filter. The 95 reads a good bit higher, even at 261K, but I haven't checked either gauge for accuracy.