Where is the MAP signal taken from? If you want to check for pulsations, you really need an O-scope. MAP line not connected properly=tube between plenum and ECU has come off at an end or has a tear in it increasing the load reading to ECU and making ECU fuel for higher load.

Been a while since I played with a hand controller but wasn't there a screen that should you sorta which cell you were operating in and how much the injector opening time is? Really would like to watch what the MAP reading shows up as on the ECU at the 2500rpm stutter.