What started as just a simple fix has turned into a puzzle and I decided it's time to solicit some input. This is a California EGR '91 245. EZK terminal six is throwing the EGR 2-4-1 code. The car has a new valve and sensor installed as well as a new pipe to the exhaust manifold and the "top" pipe is clear. All vac lines and elbows fine. All electrical tests show correct function, temp sensor is good, contacts are clear, control solenoid is working. Applying vacuum to the valve causes the car to stumble. In other words, everything in the engine bay checks out, but the code keeps coming back. Has anyone had a 162 EZK ICU fail? This is such a simple little system, component-wise, don't know what else could be bad at this point. Car runs just fine, though I'm not sniffing the exhaust. Any thoughts will be appreciated.