B27 and B28 are communication wires that run between the ECU and the MPEM. You have apparently fixed the problem or the ski wouldn't run at all.
The beep is trying to tell you your gauge is inop. Did you blow the fuse?
If the fuse is OK then remove the gauge (pops out the front) and check the connection and see if there is any water inside the gauge. Circuits 1-10 and 1-11 are the communication wires from the MPEM and the gauge. Look at those wires for corrosion at the MPEM.
Most dealers have a way of checking to see if another dealer in the country has the part you need. Just because it's discontinued and can't be ordered doesn't mean it's not sitting on a shelf somewhere.
DAWG