Has anybody else had reliability problems with the Stebel air horns? I've had 3 or 4 fail in the past 18 months...both of the compressors on my A6 are on the fritz now and I'm reluctant to order another pair... Thanks! Lee Lee Levitt '01 A4 1.8t quattro avant ''99 A6 quattro avant '97 A6 quattro avant '96 A6 quattro avant