I will take some time here to provide som input and about some things that many of us have learned over the years... Throttle abruptness is something that needs good tuning skills to refine, and not just for riding around on the street, because for racers, it's more critical than outright power... the ability to apply power at lean even if it's not maximum lean (where you may apply more than just a fraction) is very important. So don't discount the people who tune bikes for the track. One of my favorite motorcycle books was written by Troy Bayliss himself, and it's titled "A Faster Way"... he devotes a lot of time to the importance of the engine mapping/electronics part of the equation, and especially on the subject of throttle abruptness.
From my experience, addressing the following strategies/considerations are effective in this area... some can be adressed by piggy-back devices, but it's more appropriate to do so directly with the ECU:
1. Make sure that the motorcycle is healthy and working properly, and that the throttle position sensors are properly set up, that there are no vacuum leaks, that the butterflies are properly set up, and that the throttle controls are properly routed. These points are carefully looked at on a proper race bike as well.
2. Emissions... I don't want to kill any trees in this world, but there are a lot of emissions driven factors that would be eliminated on a race bike. The OEM emissions strategy is lean, and even leaner when decelerating, and injecting air into the exhaust system to further burn any hot unburned fuel escaping the exhaust during the valve overlap. This needs to be addressed.
3. Proper fuel mapping... overall the way the engine behaves is lean tends to be jerky, rich tends to be lazy.
4. Proper ignition mapping... ignition advance strategy can really soften or awaken the throttle response in certain areas. Yamaha has just recently started to address their throttle jerkyness with this with their factory tunes, but many of us have been doing this for decades. If you're ever in Phoenix, I can show you the evolution of the ignition maps and how Yamaha has dramatically improved it on their stock maps just starting in 2016.
5. Accelerator pump function... the fuel needs are different with rapid opening of the throttle compared to a slow and gradual opening... the carb days we needed an accelerator pump to add fuel for transient applications of power, and modern ECU's have strategies to mimic this... you can really feel how the engine reacts and can be coerced to behave appropriately with this function.
6. Engine tuning dynamics (cams, valve sizes, port sizes, compressions, exhaust tuning) all play a role and sometimes present a challenge, and these characteristics can be tamed with ECU tuning strategies for the most part.
7. With fly by wire and secondary butterfly systems, the throttle system can also be tuned and this is an important part of the strategy. The ECU tuning needs to be able to manage this function effectively.
Finally, there are so many parameters to change and play with that it's easy to get lost. Most off the shelf tunes I have played with weren't very good.... although they have been surprisingly consistent from bike to bike. The higher the state of tune for an engine (high compression, high RPM, aggressive cams, aggressive timing, aggressive fuels) the narrower the range is for a good tune. The RS motor for the Ducati I have has almost 15:1 compression, 40 degrees of valve overlap (that's a lot), has huge intake and exhausts, light crank and flywheel, so it's considered a high state of tune, and the mapping needs to be very precise or it will buck and surge pretty good. It's tuned to run very smooth and user friendly (I'm not that good of a rider to manage it otherwise). Street bikes with a lower state of tune are a lot easier to get right, and the range where they run outstandigly is considerably bit wider.
My Ninja 300 is tuned pretty good now, but I don't have any more than around the block once experience on the stock setup, so I'm not too familiar with your abruptness issue. On some of my other bikes it was really bad, and now it's perfect
I've plugged the flashed Ninja 300 ECU into a few other bikes to see, and it seems to work excellent, even older bikes. I have a few spare ECU's and once flashed, they also seem to interchange between 2014 2013 2015 without any issues (not the case with the stock ECU, as some of the emissions systems are a different strategy. There can always be some more tweaks depending on exhaust systems and wanting good fuel mileage, things like that... and if tuning with a wideband O2 sensor, plug or block the exchaust plates or they will throw off the wideband and cause drivability annoyances on their own.
So believe me, the abrupt throttle response you're experiencing can most definitely be managed.
