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1) All O-rings eventually die, but only some have truly lived. The upgraded ones are better material.
2) There's a lot of slop in the OEM bearings where the Vanos connects to the splined shafts, resulting in rattle. The upgrade tightens that up so it runs quieter.
3) There's a lot of slop where the exhaust hub tabs go into the oil pump disk, so the tabs hammer around in there and eventually break off. The upgrade has a new set of slightly smaller holes.
4) The solenoid pack can fail where the connector is soldered into the circuit board. The upgrade adds extra mechanical support.
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Warning: May contain traces of nuts.
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