[carmine]

Emulsion tubes that do not emulsify fuel and air very well will also give you the stop and go feeling you discribe.

Trumpets with sharp edge at outer leading edge tend to cause a lot of turbulance to incoming air entering the trumpets
That turbulance multiplied more so on the first 2 trumpets that are exposed to the scoop opening
Turn the scoop around (cowl induction) problem solved.