[Richard L]

Are there any inline checkvalves on the port injectors?

Is the AEM a direct "plug and play" replacement to the factory ECU?

I suggest moving the red wire of the grey harness to another 12V source - only active at pre-crank key position. It helps to isolate the HFS3 to the AEM.

We have many EVO users over the years, This is the first issue I heard. Let me know if the above suggestion cures the issue.