I don't run my cars in....never have.
Every new car I've owned I've warmed it up well before using the revs, and with the S3, let it cool down before switching off...I've never laboured the engine or sat on the red line and held it there...but other than that I've used them as normal with 0 miles on.
I do drive slightly more sympathetically when less than 500 miles because it's not just the engine you are betting in, but the brakes, suspension, gearbox and all the rest. Anyone who knows my driving will testify that I don't pussyfoot around, but nor do I 'thrash' or 'abuse' the mechanicals.
But basically, drive it as normal and get it used to how it's going to be expected to behave for the forthcoming years.
BTW, each car I've owned has produced above the manufacturers rated power very early on in it's life...no doubt because of the way they are run-in, and then run.
On a side note:
I have a freind with a Civic Type-R who drove like he was driving Miss Daisy for about the first 2000 miles...on a RR day it produced 10 BHP less than ANY other CTR there that day. Coincidence?
I have another friend who drives a corrado VR6...it's a town car...only used in traffic, never used up the revs...and it is consistantly producing 10 BHP less than an average 2.9 VR6 and upto 20 BHP less than a 'well used' variant. Coincidence?
To me, use it hard but treat it with respect, and your engine will make decent power all it's life.
..but it's never too late to forget how to use the accelerator pedal and undo all the good that's been done in the past!
