The power brake booster on my 1983 300SD. The whole damned car was build around this part. It took two and a half feet of extensions with swivels to get to the four mounting nuts. Even at that, it was a PITA because I couldn't see the nuts. It was strictly by feel. Replacement was as bad as removal.

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1983 300SD "Guderian"
1987 MR2
2015 Camry
2015 Chevy Spark
2006 Hyundai Tucson