Oil pickups like to be 1/4" to 3/8" off the bottom of the pan, measured with the pan gasket in place. Like Bob said, verify your dipstick. Are you running a windage tray/screen? They help control
oil in the sump. I used to run a big chevy that would lose pressure at high rpms at the top of second gear. Turned out that the high volume pump was sucking up enough
oil to cause a vortex in the oil pan and allow the pickup to suck up air, even though the pan had plenty of oil in it. I replaced the high vol pump with a regular one and the problem went away. That was the only change made at the time the pan was removed. Pressure was unchanged at all rpm's except the high speed drop which disappeared.