The PEM regulates fuel pressure by varying the ground side of the fuel pump. The longer start time was due to 0 pressure hold or rest pressure. The fuel pump had to pressurize the line to get up to pressure to start the engine. If you shut the engine off hot and restart after a short rest, it would take longer. The 0 fuel press will boil or turn to a gas state inside the fuel line due to the heat from the engine. Now you have to build up liquid fuel pressure and push gas state out thru the injectors to get back to normal spray mode. Pressurized liquid fuel in the fuel rail will stay in liquid mode after shut off. This is why the in tank check valve is needed.
Go to your VIDA to get specs. I did a screen shot of mine for you to get to the same spec location.
The P0088 code is for fuel pressure too high. Fuel pressure for your car should be 480 kPa, Duty cycle 50%.
This is why the code is set. The 20% duty is the system trying to lower the fuel pressure closer to 480. The 580 kPa before could be why the pump was noisy? The check valve is located in the pump module to hold rest pressure. When you turn off the engine does the fuel pressure hold? Not sure if the pump you got could be a problem. I would only use Volvo or Bosch fuel pumps. The PEM is working because of the 20% duty cycle. I am not sure what would be causing the higher fuel pressure before or now.

 

The PEM regulates fuel pressure by varying the ground side of the fuel pump. The longer start time was due to 0 pressure hold or rest pressure. The fuel pump had to pressurize the line to get up to pressure to start the engine. If you shut the engine off hot and restart after a short rest, it would take longer. The 0 fuel press will boil or turn to a gas state inside the fuel line due to the heat from the engine. Now you have to build up liquid fuel pressure and push gas state out thru the injectors to get back to normal spray mode. Pressurized liquid fuel in the fuel rail will stay in liquid mode after shut off. This is why the in tank check valve is needed.
Go to your VIDA to get specs. I did a screen shot of mine for you to get to the same spec location.
The P0088 code is for fuel pressure too high. Fuel pressure for your car should be 480 kPa, Duty cycle 50%.
This is why the code is set. The 20% duty is the system trying to lower the fuel pressure closer to 480. The 580 kPa before could be why the pump was noisy? The check valve is located in the pump module to hold rest pressure. When you turn off the engine does the fuel pressure hold? Not sure if the pump you got could be a problem. I would only use Volvo or Bosch fuel pumps. The PEM is working because of the 20% duty cycle. I am not sure what would be causing the higher fuel pressure before or now.

With new pump it holds pressure, 35psi when turned off for a long time. Engine starts fine and runs good.
Measured with current clamp the current going to the pump motor is 11A. Doesn't change with engine rpm and pump sound is steady.

 

Does the fuel system have a return loop? Could be obstructed...

 

All cars have return loop. This one has internal gas tank return loop.