Normal is approximately 30 to 32 cruising at 2000 - 2500 rpm and full operating temperature. It will increase at higher rpms up to around 36. Of course it drops off considerably at idle, but with the original equipment pump and cam chest components it normally ran at 10 psi. When I changed my cam plate and cams to the new style (2007 and up), idle pressure dropped to anywhere from 5 to 8 psi hot which was common on the 2007 and up Twin Cams.
My bike started showing symptoms like yours at about 20k miles, with reduced pressure at cruise and idle, thus my change to a new plate and pump along with a cam change. The old pump showed no real damage and little wear, leading me to believe it was more of a bypass valve sticking open issue than a pump worn out issue. I recommend updating to the later style higher output pump and plate with hydraulic chain tensioners.
Jerry