Wow, you usually don't hear about those going bad. That's very odd, but I'm glad you've got it sorted now.

 

How does the ecu cause low fuel pressure?
That's a new one for me on this bike.

 

i also put in a new fuel pump fuel pump was on its last leg i guess. One more question my buddy totaled his f4i an wanted to know will a f4i ecu work on 929rr if so was gunna get it off him for a spare his ecu number is 38770-mbw-a12

 

No, not even a little bit would that work. It'd be a horrible idea.

The ECU is what controls the motor. Your 929 engine doesn't want to churn 14.5k rpms. The fueling would never be correct because it's a 600, it wouldn't even be close.

And all of that assumes the sensors and everything will hook up, too - which they probably wouldn't. I'd be willing to bet some of the sensors are different and the plugs don't all hook up with each other.