Residual pressure is very important for proper hot restart. What you are looking for here are leaks in the system. When you shut down the engine or fuel pump the system pressure will fall to 2.4 to 3.0 bar and stop. Pressure will slowly bleed off over time from there. If the pressure falls too quickly look for problems in the accumulator, fuel pump check valve, and fuel pressure regulator. On the Bosch KE-jet system it is very important to have “Free Play” in the airflow sensor plate or the piston in the fuel distributor will not rest on its seal and you will have a leak down through the piston into the intake manifold.