I go by the simple mode of 10 psi per 1000 rpm , but  I can't confirm
the 50 psi at 5k.  My Boston Bob motor has nigh on 100k on it and has
similar OP to Ken's readings.  I wonder how much higher the cold
start up pressure really is, since my VDO gauge only goes to 70.  I
have a 0-100 VDO gauge, but I was saving it for a CS injection system
where you need to see above 70psi....

DM&FS