If your Error 3 is only flashing up on a closed throttle and then disappearing as you openup then you've nothing to worry about.

It's not right though, so what you wanna do is to get in there and do some adjustments.

Take off the airbox and look at the right side of the right hand carb. You'll see this little round black thing. That's the throttle position sensor (TPS). Basically a flash name for a 5K potentiometer. There's a small (special torx head) screw holding it in position. If you ain't got the proper tools for the job then a pair of long nose locking pliers can usually persuade it loose. Then with the ignition switched on (engine NOT running) slowly turn the pot anticlockwise until the Error 3 light goes out. Nip up the locking screw...job done.

There are numbers for the correct setting, but I ain't got around to writing it all down yet.