M,
I don't know about the SBR in the ad but I have a 3.6L Boxster S for sale that would kill this SB and keeps up with 911 GT3's J stock PCA. It has tons to offer for the price.
Don't want to highjack your thread so PM if you'd like to learn more.
Here is a link to the car here on the 986 forum.
FS: Boxster S 3.6L Race Car
Thanks