I'd say the problem is in the ECU. That's the brain box that controls the fuel injection.

There's no fixing an ECU. If somethings wrong, you replace the box. They're outrageously expensive to buy from a dealer. Somewhere along the lines of $1,600-1,800.

I have a 200EFI and mine went bad last year. I found one on the internet for $200. It came with a guarantee to work upon installation. I put it in, and the engine has run perfect ever since.