Hi there Sinisa,
I think you're correct surmising this cowling stems from a later date then September.
www.flickr.com/photos/28092068@N03/12373461183
The position of the Kaltstart vane access hatch, in-line with Kurvel hole on the starboard side, does indicate a DB 605 D engine, which you do find only in Bf 109 G-10's and K-4's. The camouflage pattern is quite consistent with what we can see on Erla Leipzig produced planes.
After checking known Bf 109 G-10 losses, the first lost in absolute was indeed a JG 4 machine, on 2 November 1944: Bf 109 G-10 W.Nr. 490 396 "Schwarze 5", Uffz. Karl-Heinz Jessen, 10./JG 4. Source: Mombeek 2000, p. 248.
This implies the engine cowling you are looking for was not flown in combat before late October 1944 at the earliest, and November as proven.
Let's hope we'll hear some more about the plane it stems from ;-)
Cheers
Marc