915 is Fuel Pumps

Interesting that you mention this. Both of my 915 fuel pumps failed at 138 hours. The pump assembly is at Lockwood Aviation awaiting new pumps, of which there is no delivery date as of yet. Also, in conversation with Lockwood tech support, this is a known problem with 915 fuel pumps. 

Well maybe switching out fuel pumps  THREE times in 140 hours of service is acceptable for this company. Read the latest information they released on this sounds like denial and no acceptance THEY ROTAX have a problem. The next pilot may not be so lucky and make it to the airfield they know we are flying with these pumps and they are JUNK. This is in the new letter sounds like they ok to have Rotax name on it. But claim it not part of the engine but the aircraft manufacture

WARNING

The fuel pump assy. is part of the fuel system on aircraft-side and not a
part of the Engine Type Design. The fuel pump assy. has been tested and
released by BRP-Rotax, but it is not certified. The correct function in con-
junction with the entire system and the certification of the fuel pump assy.
is the responsibility of the aircraft manufacturer and must be carried out
jointly with the aircraft

There is nothing new here.
You are reading too much into this.

The fuel pump assembly. is part of the fuel system on the aircraft-side and is not a part of the Engine Type Design.
The fuel pump Assembly is an engine Accessory, just as the Fuel Tanks, Radiator, Oil Tank, and Oil Cooler are accessory items whose installation is beyond the control of Rotax.

The fuel pump assy. has been tested and released by BRP-Rotax, but it is not certified.
The entire engine has been tested and released by BRP-Rotax, and it is also NOT certified.

The correct function in conjunction with the entire system and the certification of the fuel pump assembly is the responsibility of the aircraft manufacturer and must be carried out jointly with the aircraft.
The installation and plumbing of the Fuel Pumps are obviously beyond the control of the factory.
It would be unreasonable that they would be responsible for certifying how they were installed in any particular Airframe.

- - -

This is not saying that there is nothing wrong with the pumps.
This is just legalese reminding you that the ultimate responsibility always lies with the Aircraft Manufacturer/Owner and/or Pilot in Command.

Does Rotax specify a particular pump is to be used, or do they provide pump specifications and allow the aircraft manufacturer to select the pump?

Rotax makes Fuel Pump Assemblies available as Accessory items for their engines.

It "Appears" that Rotax has Pierburg modify and re-brand their pumps.

The 914 Pump appears to be a modified Pierburg 7.21440.78.0 Pump.
The 912is/915is Pump appears to be a modified Pierburg 7.21287.53.0 Pump.

Both Rotax branded pumps have different Connection Ports and Electrical Connections than the OEM pumps.

If you have an Experimental aircraft, you are free to use whatever pump fits your fancy.
The Turbo will want 1bar of nominal pressure, and the fuel injected engines will want 3 Bar nominal pressure.