IAT > Inlet Air Temperature
CLT > Coolant Temperature

Boost PWM - Ignore, not used for this application

Trigger In > either once per crankshaft revolution, which will cause two injection pulses per cycle, or once per camshaft revolution, which will cause one injection pulse per cycle.
The trigger pulse could come from either an inductive magnetic pickup, or from a Hall Effect sensor. The Killer instructions should explain all of this.