I installed a Raptor FRRP on my 2002 Cummins 5.9 ISB. It's in a 38' diesel pusher motorhome. Idle pressure out of the box is 15 PSI. WOT is 10-11 PSI, cruise is 12-13 PSI. Should I turn it up a tad? Looking for what pressure is optimal for power and cooling of the VP44.

 

I would turn it up. Bosch specs the pump at a minimum of 10psi. I wouldn't run less than 15 at WOT.

 

Turn it up 2-3psi and get a big line kit to get rid of the banjo bolts that are so restrictive.