Do or Don't I monitor fuel pressure in a about to be fitted brand new 915iS

I’d monitor fuel pressure for sure on the IS series. There’s no mechanical pump and pressure is critical for the fuel injection system. 

Hi Peter, You defiinitely need to monitor fuel pressure on the 915. It does not get reported from the ECU / CANBUS so you need a sensor in the fuel line, typically close to the fuel rail. Unlike the 914, if the fuel pumps are turned off the 915 stops immediatley. Fuel pressure and run up checks certainly need fuel pressure monitoring.

Monitor fuel pressure

I agree.  Rotax has an SI that describes the installation process in their technical documentation library.   I really don't know why this just doesn't come standard when you purchase the engine.  I have a second pressure sensor at the inlet of the fine fuel filter to monitor fuel restriction and flag replacement of the filter.

Eric I would be very interested to know if you see a difference in the inlet pressure between 1 or 2 pumps running. This might help resolve the contentious issue of which scenario is best for avoiding "vapor lock".