I just saw the following posted on Facebook:

http://www.roadandtrack.com/car-videos/this-is-probably-the-flat-four-cayman-at-the-nurburgring

I also posted awhile back about the fact that Porsche was considering using the flat-four layout in upcoming engine options for the Boxster and Cayman.

I then saw the videos provided on that page.  First, they posted a baseline video, so that people know how a current Cayman sounds:

Then, they posted a Boxster andCayman with what’s unarguably a flat-four motor:

I prefer the sound of the flat-six, but the flat-four isn’t bad.

EDIT:

There’s quite a bit of uproar with the Porsche “purists” on R&T’s Facebook page…check out the comments: