i've got an a4 1.6, with the engine code 'AHL', a replacement lump is proving hard to find, the year before my motor (r plated 98) the eng. code was 'ADP'. What i want to know is if they are interchangable, that is take an 'AHL' out of my car and put an 'ADP' back in? i have the earlier lump lined up and am just waiting to know before buying it. thanks for any input