A bit high negative long term fuel trim at idle

Hi, i've a fiesta st 1.6 ecoboost with sport cat, full catback exhaust and remap. (Sorry for my bad English, i try to do my best).
The car starts fine with no hesitations but i noticed but it idles a bit rough when it is cold, it stay at 1200 rpm as it should do but it randomly bounces up, then gets steady at 750rpm as it gets warm, i hear the exhaust sound is not smooth, it is a bit irregular.
The car doesn't smoke at all in any conditions, exhaust smell it is normal.
The car seems driving fine, smooth, no hesitations and pulls good, maybe sometimes it looks more powerful and torquey other time less powerful.
I did some tests:
Misfire (forscan test mode 6) shows 0 counts for each cylinder (at idle, at 1500 rpm, at 3000 rpm, wot, cruising etc..)
CO2 header tank test was ok.
No overheating problems nor leaks of any kind.
Spark plugs changed last summer, oem ford, 6000km done at the moment.
Battery is ok.
Maf is reading good and cleaned, air filter is new.
O2 sensors test with forscan and torque pro shows they are ok.
It seems all good but long term fuel trim shows from 10 up to 16 % negative at idle (short term near 0%) and as soon i hit the throttle it goes down to -5/-3 %..when i'm cruising or full throttle it stay around -4/-3 % negative meanwhile short term is close to 0% or a bit positive (no more than 3% positive).
What can i check?
Got several logs done with forscan, but unfortunately i can't post here, they are fsl files.
I can only post a screenshot of torque pro showing -15 ltft ai idle.
Thanks for your help.