Mercedes Benz repair: 560SEC 1988, fuel pressure regulator, intake manifold gasket

Question
Idle jumping at stop, but car runs smooth ?

Answer
Questions:
How many miles on vehicle?
Has fuel filter been serviced?
Any alterations to vehicle?
Any service history on vehicle?
Please describe full power acceleration and shifting from stop.
Please describe engine compartment condition = clean/no corrosion, some light rust and corrosion, heavy surface pitting and/or holes.

Possible answers, further diagnosis needed:

#1. Check charge voltage.
#2. Test battery.
#3. Check for vacuum leaks on the engine.
#4. Vehicle running; listen at exhaust for sound like plugged up vacuum cleaner + very weak air flow.

Generic list of all possible parts that could be your issue:
This list will shrink with further data.

Altitude Sensor
Alternator
Battery
Catalytic Converter
Cold Start Valve
Cold Start Valve Gasket
Distributor Cap
Distributor Rotor
E.H.A. Valve
E.H.A. Valve Seal
Exhaust Valve
Fuel Distributor
Fuel Distributor O-Ring
Fuel Injector
Fuel Injector Seal
Fuel Pressure Regulator
Fuel Accumulator
Fuel Filter
Fuel Screen
Fuel Pump
Fuel Tank Vent Valve
Fuel Pump Relay
Idle Control Unit
Idle Control Valve
Ignition Coil
Ignition Wire
Intake Manifold Gasket
Intake Valve
KE Control Unit
Kickdown Switch
Overload Relay
Oxygen Sensor
Oil Pump
Reference Sensor
Spark Plug
Spark Plug Connector
Throttle Body Gasket
Timing Chain
Timing Chain Tensioner
Timing Guide Rail...
Voltage Regulator
Water Temp. Sensor