I have not done this conversion but I believe Todd reflashes the 986 7.2 DME to run variocam plus effectively, and 987 3.4L headers are a direct bolt on. So yes it is possible to do this for a lot less than 25K. Ask him. He has done all three conversions successfully. He has a 2001 986 3.8L available for sale now. http://986forum.com/forums/members/tholyoak.html
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2009 Cayman 2.9L PDK (with a few tweaks)
PCA-GPX Chief Driving Instructor-Ret.