First, start at the beginning and carefully diagnose the problem.
What is wearing excessively? Front or rear tires, inside or outside edges?
What suspension system was added exactly?
What are your current alignment specs?
Only when these questions are answered can we make useful suggestions other than vague wild guesses as to a solution to your problem other than: "Return it to stock".
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2009 Cayman 2.9L PDK (with a few tweaks)
PCA-GPX Chief Driving Instructor-Ret.
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