The carburetor on the engine in the pictures is the original Tillotson that came with the DLE30, it just has a Walbro pump cover on it with the external pulse fitting.

Anytime I mount an engine with the carb through the firewall I always make provisions for ventilation at the rear of the fuselage. Where you get pressurization problems is when manufacturers cut lightening holes in the front fuselage bulkhead around the engine box, people that don't tape over those holes or don't provide an exit for air at the rear of the fuselage are rolling the dice every time they fly, IMO.