"A captured Spitfire Mark Vb fitted with a Daimler Benz DB605a engine. The modified test plane exhibited superb handling characteristics melded with the higher engine power and speed of the German Daimler-Benz engine. Originally a captured Spitfire Mark Vb (EN830/NX-X) that accidentally landed on the Nazi occupied Channel island of Jersey on 18th November 1942. It was taken to Rechlin, Germany within a month of its capture. It would be given the code CJ-ZY and painted yellow and green. A number of changes were made to the Spitfire, firstly its 12 volt electrical system was replaced with the Luftwaffe's 24 volt one. The Rolls-Royce Merlin 45 was also removed with a Daimler-Benz DB 605A engine installed. It would then be sent to Echterdinged, Stuttgart where a propeller and carburettor scoop from a Messerschmitt Bf 109G was fitted. Also significantly, the original guns of the Spitfire Vb was removed."
I've read about this! The German test pilots said that the bastardized plane performed better that either a regular 109 or the Spit.