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					Originally Posted by JFP in PA   Just out of curiosity, why are you using a GT 3 master? | 
	
 
JFP,
It seems to be a popular mod by the guys that track their Caymans, reporting a much firmer brake pedal.
However, I have not replaced mine (yet)... 
The master cylinder for the GT3 has a larger diameter than the standard CS master cylinder.  On the Cayman website (Planet9) they have the different part numbers for the masters
.