My ninja loses power in the wind

I really need to know what size engine you have in your Beretta as well as how many gears are on the shifter as in low one low two Drive with a circle around it or one two three drive with a circle around it sounds to me like a torque converter pressure switch when vehicle is shifting into overdrive switch is not operating correctly releasing pressure from torque converter causing vehicle not to have enough counterweight for transmission until vehicle slows down and then will operate again shifting through gears until the Overdrive goes to kick in send more info

P0340 code means "Something" is wrong in the timing...
from CMP (Camshaft Position sensor) to the crankshaft bolt.

Very first thing, verify connectors are clean and shiny.
clear all codes, even hard codes.

I'm going to assume you have the 3.4 V6 engine which uses direct ignition with a coil on each plug.
Could be ignition or fuel related.
A weak spark/coil will allow the engine to run on all 6 cylinders at idle but miss under load, especially when going into overdrive at 45 mph. Not enough spark to jump the gap.
Same thing with low fuel pressure or dirty injectors. Not enough fuel when the engine is working hard.
Usually when you get a hard miss you will get a trouble code for the cylinder that is not giving power.
Have you changed the fuel filter in the past 12 months ?

engine is getting enough fuel at low revs,starved when opened up fuel filter suspect,clean out and test

YOU HAVE A TORQUE CONVERTER LOCKUP ISSUE, HAVE SOMEONE LIKE THE DEALER,AUTO ZONE OR IF YOU ARE HANDY CHECK FOR CODES, NO CODES....THEN TAKE THE CAR OUT STEADY DRIVE AT AROUND 45 MPH, GENTLY HIT THE BRAKE PEDAL JUST ENOUGH TO MAKE THE REAR BRAKE LIGHTS GO ON BUT NOT HARD ENOUGH TO STOP THE CAR...DO YOU FEEL THE CONVERTER SHIFT IN AND OUT EACHJ TIME THE BRAKE PEDAL IS TOUCHED MAINTAINING A STEADY 45 MPH SPEED, IF IT THAT SAME SHUDDER YOU ARE FEELING THE TORQUE CONVERTER NEEDS TO BE REPLACED, NOT AN EASY JOB AS THE TRANSMISSION HAS TO BE REMOVED TO GET AT IT.SORRY ABOUT THE CAPS.......

Sounds like low fuel pressure. i.e. fuel pump, fuel pressure regulator, or fuel filter.

Hi,
The air cleaner mighty be clogged causing insufficient air supply. That is why it runs fine on idle because less air is needed and when the engine demands for more air, there isn't enough.