Leonard Bernstein's love-hate-relationship with Wagner is well known. He once said that he hated Wagner on his knees. This ambivalence is shared by many Wagner lovers. Late in Bernstein's career he often turned to Wagner. Two of the most important events were the Vienna Wagner concert in 1985 and the six Tristan concerts in Munich in 1980/81. The last resulted in a CD release.
Here is a clip from the Wagner concert in Vienna: Siegfried, Act 3.