3406E warms up looses boost ?

[Mal4shtf]

Ecm circuit boards see alot of heating and cooling cycles. Typically an ecm fails on the injector driver side which is where all the high power and heat is generated. Solders get weak after so many cycles. It can cause this and I'd be leaning that way if you've done all the other listed approaches which you have. I'd bet that ecm gets warm after a few miles of load and doesn't drive the injectors enough. I'd caution driving it like that because a bad ecm can cause improper fueling and tulip the valves eventually resulting in a dropped valve. Catastrophic. There are a few companies that can bench test the injector driver as well as the regular circuitry of that ecm and you can find them on Google. The one I use (can't remember name) has locations in Texas and Florida. Make sure whoever you send it to can bench test the injector driver. You may change injectors anyway.