Hi, I just wanted to come back and tell you that it's fixed now. I printed new ducts which made it much better, where before it was up to 15-20° C drop at maybe 50-60% fan speed, with the new part it's more like 8-10° drop at 100% and fast recovery. Then I also did the PID tuning (at 50% fan speed), it overshoots more and oscillates a bit with no fans, but recovery is in a matter of seconds, drop is reduced and with fans on it's very stable.
So all in all a good result. Thank you for your help.