System Check
WARNING: This page is about a different car, the 1994 Mazda RX-7. However, it is still accessible from the selected car via links, so may be relevant.
Check all connectors and hose routings. Check for cracks, leakage and restrictions, and repair as necessary. Start engine, and ensure diaphragm of EGR control valve does not move while engine is cold. Warm engine to operating temperature and allow it to idle. Ground Blue/Yellow wire at EGR solenoid. Ensure EGR control valve moves and engine idles rough or stalls. If no movement occurs or engine idles smooth, test EGR components as necessary.