p0400 service engine soon on 1998 Chevrolet Metro

Idle started going up and down worst when head lights in on position. Then service engine soon light came on. took car too jiffy lube hooked up to computer came up p0400

Asked by for the 1998 Chevrolet Metro
Diagnostic Trouble Code (DTC) P0400 stands for EGR Flow Malfunction. Sometimes this code is set when the Manifold Absolute Pressure Sensor detects a pressure change too small or too large.
Can u help with a location for this pressure sensor. Idles getting worst but runs fine.
Thanks Rob
The MAP sensor is located on right side of firewall.

Replacing the MAP sensor could not be the solution. There are more variables that could set the DTC P0400. Some diagnostics are;
*Check all vacuum hoses connections, inspect for leaks, clogs or incorrect routing.
*Check for malfunction in the EGR solenoid vacuum valve or the EGR by-pass valve.
*Check for a poor PCM electrical connection.

Get help from a qualified technician, find a shop or mechanic here;