to be honest, I've ordered MANY a kit from e-bay, for about $60 shipped to my door, and have had no issues with any of them. I've installed over 10 sets of these in the last 3 years and neither my car, nor anyone elses is showing problems.
You do not need to spend a fortune.

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I swear, my cars are like a girlfriend.
Sometimes its a rough ride, sometimes its smooth motorin'.
Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
BUT at the end of the day, she loves it when I am inside her.

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'91 850i
'05 X5 4.4i
'09 Clubman S