To disable set TPS thershold to 100% and MAP threshold to 510kPa.
To enable this function there are some steps to follow:

• Set up correctly your primary injectors in the injector settings dialog.
• Staging injectors appear in the injector output table in the rows following the primary injector groups
• The Number of staging injectors are:
•    for 1 Primary Injector: 1
•    for 2 Primary Injectors: 2
•    for 3 Primary Injectors: 3
•    for 4 Primary Injectors: 4
•    for 5 Primary Injectors: 2
•    for 6 Primary Injectors: 2
•    for 7 Primary Injectors: 0
•    for 8 Primary Injectors: 0

Transition Fuel Trim
After activating staging you can trim +/- 2048us injector pulse width to both injectors

Rate to primary injectors
Same size = 100%, Smaller secondary stage = lower number, larger injectors = higher number, 630 primaries with 1680 secondary = 266%

Example:

number of Primary injectors = 4,
Rate to Primary Injector Size = 100%,
injector 1 pulsewidth = 10ms when staging not active,

   after activating staging injector 0 pulsewidth will be 5ms

number of Primary injectors = 4,
Rate to Primary Injector Size = 200%,
injector 1 pulsewidth = 10ms when staging not active,

   after activating staging injector 0 pulsewidth will be 3.33ms

Thresholds:
Secondary stage is activated when both TPS, MAP and RPM thresholds are exceeded.