I think that may be because under idle you should be pulling 15-17" vacuum which drops the fuel pressure, at least is does on mine...or did you take your reading with the hose off the regulator? Just a thought. I get 30psi in run position, start the car drops to 26psi, pull the vacuum off I get 37psi, stock regulator. Stock pump and harness I think, haven't checked. 
