Since I bought the car is had P0400. While I was lucky to have its sister I took the egr valve. Hoses and throttle body and installed them on the one with egr codes. Same issue. When I switched the supposedly bad EGR into the other car, it worked fine. So that eliminated EGR valve itself issues. Checked for vacuum leaks, electrical connectors, all fuses, and relays. No luck. Any suggestions what’s next.