I have a mint low km 86 gx

90km orig

ran dead cold and perfect until one day it overheated.
I replaced thermostat, radiator, did a flush and bleed ,
and no longer over heats. but since then I cleaned the engine
bay a bit, and driving since then the car had hesitated .

could I have damaged something over heating ?
could I have knocked something cleaning bay?

it hesitates at 6000-7000 roughly

doesn't sputter , only power loss.
doesn't smoke whatsoever
doesn't have any idle issue whatsoever
consistently 6000-6500 rpm where it starts
does it in neutral not under load
makes a minor whistle/hiss sound when hesitating
pulls very hard and runs perfect in all gears and all rpm
except 6000+
exhaust gets a bit quieter when hesitating as if not burning as much fuel

car is stock except koyorad