Controller arrived on Friday and was installed on Saturday. Works great. I actually have used it operating in a differential pressure mode with a flow probe prior to the filter on the return and a flow probe about 2/3 of the way down the main duct (as I was taught for VAV systems).
I’m very pleased with how this works and it has solved the control problem I was dealing with. The Bosch airhandler in the installation is capable of two speeds, but of course the ECM 4Z doesn’t care about those. One possible improvement for your controller is to allow for a different HI set point for Stage 1 and Stage 2 call. Stage 2 could be at a higher TESP, which would be a bit noisier, but generally wouldn’t be used. As is stands the ramping up of the fan is gentle and not very noticeable unless you listen for it. Much better than before.