it says use a 10% solution of citric acid (100g/l) in the service manual (20-015 under the engine section on the CD) to flush it out. I used it and used only 5% and it still did pretty darn good

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2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/showthread.php?p=852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP