Hi folks,
Well, I have an update on my woes with a 2005 STX 12f.
Here was the original problem:

Differences:
1) When I turn the key switch ON, the display didn't beep at all, but the display went through the self-test in the right amount of time
2) The display registered 0 MPH all the time.
3) The ski won't rev past about 5000 RPM (seems to be some sort of limiter cutting in), and confirmed it is not in SLO mode. The 5000 rpm is reached at about 1/4 throttle, and won't go any higher all the way to WOT
4) All other display functions on the ski seemed to work correctly
5) The spark plugs look like it is running rich. Could that be related to a timing or EFI issue?

I have had some suggestions that the source of my problem is the display/meter assembly computer. It was suggested that the display/meter assembly computer, which takes in the speedometer signal, also sends a feedback signal to the ECU (the engine control computer).

I did a few of the diagnostic tests suggested in the manual, and the end result is that it says "change the meter assembly module". (For instance, the reason the speedo isn't working is that it isn't getting a supply voltage out of the display module, same with the beeper).

OKAY, so I bought a new display computer (pricey mother). After installing it, the display now beeps during the power-on self test, and the the speedometer now works!

BUT, the ski still won't go to full speed. It won't rev past 5000 rpm, and it reaches that at 1/4 throttle. Also, it doesn't seem like it likes to idle. It will idle for 2 or 3 seconds and then stall.

Any ideas of where to look for the next problem???

Could this be the ignition computer????

Any help appreciated. Thanks, E.[/align]