My 1995 Mercedes S320 has 192,000 miles on it.I opened the hood and can hear a hissing sound coming from the engine like their is a air leak somewhere.The rpms started bouncing a little bit at idle,but nothing to high.The car will also start to shake a little bit if the initial acceleration is too much and to fix this I will need to turn off the car and then turn it back on.There is no power loss and the car still drives and accelerates properly.Any ideas as to what this could be.

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1998 S500
2006 E320 CDI
1963 220S
1994 S500
1995 S500
2005 BMW 545i sport
2007 GL320 CDI
2007 ML320 CDI
1991 Toyota Previa White over Blue
2000 Lexus RX300 White over Beige
2008 Audi Q7 Black Opal over Grey
1993 Toyota T-100 Silver over Grey
2002 Chevy 2500 Express White over Grey