I think i'ts a Erla-built G-14. Photo isn't of the best quality, but fortunatelly something is still visible.
The presence of PR 16 loop antena [4] just behind the canopy eliminates a K-4 subtype.
The plane has DB 605 A-serie engine. The pipe leading to the oil vapour separator comin' through right engine bearer [1] as well as cold start push-pump button located below the bearer on a metal strip [6] eliminates D-serie Motor.
Lack of the redesigned cowling bulges as well as unpainted area [2], where MG 131 bulges were located eliminates the AS engine too.
This plane has Fo 870 oil cooler, not a deeper 987 one [7]. One can see it's more "square" lower shape. This Gustav has older type of prop, not a wider one for G-10, G-14/AS or K-4 [8].
As I can recognise in this blurry photo, there's a battery-box aft the armour plate in cockpit - the sign that aircraft has a MW system instaled [3]. There is also a blurred dot, that looks like Erla-style MW-50 stencil on the right fuselage side.
The tail wheel leg is tall one [unmarked arrow
] and the AC tires are bigger, 660x190 ones with large bulges on the wing [5].
This feautures are quite common for a late Erla G-14.
Wish I could see the oil tank. I bet it's bigger, 56l. one...