[Gaz64]

Olddog,

If it is only a dry film of "fuel carbon", I wouldn't be too concerned.

The reason you're getting it is because you don't have carbs to keep the runners clean AND you have reversion from a higher overlap cam.

Technically your system would be sequential, but as to when the injector fires in relation to the valve opening period is something to discuss with the injection manufacturer.

Even if the injector truly fires only during inlet open period, you will get some air/fuel mixture blown back into the manifold at low to medium engine speed.