P0171 and P0108 Fault Codes on 1998 Dodge Voyager 3.0L Engine - Engine Unstable, Vacuum Leak Diagnosis

I'm experiencing engine instability and failure to run smoothly in my 1998 Dodge Voyager with a 3.0L engine. After starting the vehicle, the engine runs roughly and eventually stalls. I've already replaced spark plugs, ignition coils, air filters, and distributor cap, but the issue persists. The check engine light is triggered by codes P0171 (System Too Lean) and P0108 (Manifold Absolute Pressure Sensor Range/Performance Problem). Based on my readings, when the engine is off, the manifold pressure is 76 kPa; during idle, it drops to 36 kPa. This significant drop suggests a possible vacuum leak. I suspect either a vacuum leak in the intake system or a malfunctioning MAP (Manifold Absolute Pressure) sensor. However, I'm unable to locate the exact source of the leak or confirm if the MAP sensor is faulty. Can anyone provide guidance on how to diagnose and fix this issue? Any experience with 1998 Voyager 3.0L models with these codes would be greatly appreciated.