Does 912iS need after market fuel pressure sensor?

You'll have to source one. Rotax assumes that the pumps are delivering at the proper pressure for the injection. It si important also that if you install one that it measures with the airbox pressure as baseline. I have a MGL iEFIS, and use a UMA fuel sender. 

You will need to obtain a Fuel Pressure sensor that is compatible with your display.
The UMA Brand N1EU70D Sender is compatible with most Displays.
It is a Differential sender as needed for the Fuel-Injected engines.
There is a mounting screw on the airbox that can be swapped out for a barbed fitting to connect to the Differential port of the sender.

The ECU does NOT Provide ...
Fuel Pressure Data
Fuel Level
Battery Voltage
Charge Current

The engine Fuel Rail terminates at the Fuel Pressure Regulator.
So, you will need to obtain the Fuel Pressure Sensor/Sender, but NOT the Fuel Pressure Regulator/Valve.