With that hesitation I would think you either have a dirty or bad injector that needs cleaning/backflushed or the fuel pump is weak or the strainer screen at the base of the fuel pump is partially clogged. Have you checked both of these things.
Quicker throttle response can also be achieved by removing the second butterfly in the FI unit. This can be done by removing the seat and ECU hold down plastic bracket and going in at it from the top after removing the FI units top hose clamp for the removal of the rubber neck through the hole in the airbox.
This could also be an issue with the TPS (Throttle position sensor) setting, that could need adjusting or at least checked. You need a set of test leads and a multimeter to do that. I believe the TPS setting for our bikes is .78 -.80 with the throttle closed.
To adjust the TPS you need a set of test leads, they have a set for KTMs that work on our Keihin FI system that connects to the bottom TPS terminal on the FI Unit and the other end fits on the wire harness plug on the FI units lower right hand side.
This test lead has 3 pairs of wires of which only 1 of the wires is required to read the TPS Voltage, that you can get the TPS setting with the throttle closed at the Idle position is all that's really required.
Slavens Racing sells the test leads for about $33.00 that I am talking about. They have 3 different versions of these leads so you will have to pull the plug off the TPS terminal to visually match it up to the pictures of the 3 different plug types on the website.
I'm thinking about getting a pair of these test leads myself as they will likely work on my Husky FE 501 as well. But I can reset my TPS and read its value anytime on my laptop since I run the Power Commander 5 with Autotune on my G450X.
Here's the link for the TPS leads: https://slavensracing.com/shop/throttle-position-sensor-adjustment-tool-ktm
If the idle setting doesn't fall into the range on "David Bates" video there is a lock screw and adjustment slot that allows it to be adjusted, but this is a bit touchy and barely needs to be moved and even tightening down the lock screw once adjusted can make it move a slight amount .
As for the Fuel pump filter screen strainer you can see it in the picture below. It sits at the base of the pump and comes up along its side. If the bike has sat for any length of time prior to you getting it, it can clog with deposits with today's shit ethanol gasoline.
Sorry the picture is sideways as I was at work when I sent the picture from my phone to my work email at my desk to download it to the forum for you.