Loses fuel pressure when parked

hello bimmerfest i am new to the board but have used many tips from the board. I would appreciate any suggestions. I have a 97 e38 with m62 motor I recently changed fuel filter and two weeks later my car would lose fuel pressure after sitting for 5 minutes or so. I went under the car and noticed while the car was running the fuel line had plenty of pressure soon as i turn the motor off withing 5 minutes it would lose pressure. Trying to fix this i have changed the fuel pressure check valve in the tank, the regulator and fuel pump. After car cranks for a while it starts and runs perfect! I have noticed no gas smell coming from from the lines or around the car. Please help. Car has 250,000 and runs great!
i have also changed osv, cooling pipes, intake man gaskets, and crank position sensor.