I can't give you any mechanical advice about the problem, but I can advise to you find another mechanic. Obviously this guy is diagnosing the problem by trials and errors at your expenses.

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1991 420SEL Project Car (Completed and rides beautifully) http://www.peachparts.com/shopforum/showthread.php?t=112321
2000 BMW 740IL
2000 Integra Type R - Track Car - SOLD
2005 S2000 - Track Car
06 C230 Sport
89 560SL