2023 KTM 350sx-f decel pop

Have you checked your valves?

I have a buddy with a 23 XCF 350 with no popping issue. I myself have a 23 450xcf with no popping issues. I would change the inline fuel filter and check the valves before throwing money at an ecu tune. 

Is your cold start button stuck in?  That would definitely cause decel pop. But you would get a high idle too. Doesn't hurt to check. Normal position is out on Ktm. In is “cold start”. You can also shut it off by chopping the throttle. 

High percent chance can correct by adjusting TPS. All you need is a voltage meter, a TPS dongle, and know what the voltage spec should be. 
Tpstool.com 

Doesn't it just crack the throttle open slightly when activated? I didn't think it changed the mixture in any way. 

Possible exhaust valves have not fully seated? And a bit more break-in could resolve?

I have the 2023 Husky FC 350 and it has the same decel pop.  It is defiantly in the tuning and nothing wrong with the bike.  I now have 12 hours on the bike. I  have added the twin air Hi-Flow filter cage and an FMF 4.1 exhaust and it has  greatly reduced the decel-pop. I also noticed keeping the bike a gear higher reduces the decel pop and bike has plenty of power to do so.  

95% you can correct with a TPS Tool. Look them up online, allows you adjust the TPS and I have fixed several this way. 

actively looking into it myself:

https://www.thumpertalk.com/forums/topic/1077085-the-tps-adjustment-thr…

I would check what others have stated as far as TPS and in line fuel filter....I have a 22 Husky 350 so I never dealt with this. However, I will say, a Vortex ECU mapped by Twisted will blow your mind away with how much it wakes that bike up and just cleans it all up. It would not be a bad investment and if you can't tell a difference, you can always sell it as it will work with a bunch of other bikes, would just need to be remapped.

Check the header pipe seal carefully.  

My buddies 22' 350 had an insane amount of decel pop. He did a full fmf system with a JD jetting tuner and it mitigated the issue. 

I had that problem with my '19 350SXF. I ran 93 octane non ethanol fuel to help. I had my OEM ECU remapped at Twisted and that pretty much eliminated the problem.

Try setting your idle up a little.

This 100%

Any leaks on the exhaust system can actually let oxygen get into the headpipe since the exhaust flow is a wave and flow rate is low on decel there is times when it can pull in fresh air.  Anyways once this happens the air mixes with any excess fuel from combustion and ignites, hence the decal pop. 

Seems like tps settings are kinda inconsistent with the new KTMs. Not saying that’s the issue here but lots of other threads about tps voltages being off.

I just bought a brand new 24 350 sxf and noticed this. Sounds like a standard issue with these bikes

My 23’ did this also.  Very annoying!  I bumped the tps voltage from .52 to .56.  Decel pop completely gone.  Less flameouts also.  I think the bike comes a little to lean from the factory.

I am currently going through the same issue with my 24 gasgas mc350. have done fuel filter, air cage, and fmf factory 4.1 exhaust. Still popping under decel. I will look into changing the tps setting. 

100% Correct  every KTM I've had since 2013 I have to adjust the TPS and it fixes the problem every time 

If the exhaust gasket at the header pipe has a leak, cold air gets in and will cause a pop.