There's this guy I know who has one of them fancy gold ones and he was telling me a story about one of the side effects of wearing this kit. It's kind of inverse to what RWH mentioned in that it actually makes you run faster.
So this guy I know, he was jogging around Regent's Park at ~7:15 pace and he gradually caught this guy in front of him. He passed him slowly and the gap gradually opened up. Next thing you know he hears footsteps and breathing closing in which annoyed him as he was just out for a leisurely jog and didn't want to have to defend his advertised time. The pace picked up slightly and got down to about 7 min miling but the guy still was there. He would have thought the "sub 2:30" on his back was enough to deter anyone from trying to pass him but it didn't seem to. To cut a short story long, this guy I know, well, he decides to drop in a "sub 2:30" pace mile to show this other geezer the goodness of the gold. Said geezer didn't have long to think about it after that as he was blown out the back door.
So be warned, wearing it can make you go one of 2 ways. Sit back and let the numbers taunt knowing that you know that they know that on your day you'd have them for breakfast (a la RWH), or the less subtle approach, to explicitly demonstrate said pace (a la this guy I know).
In addition to this, I now know that "this geezer" was actually one of Dan's QA runners who are out there to try and bust any imposters who claim undeserving colors. When they spot someone sporting a Xempo color, they chase them down until the subject has demonstrated they can run at least 1 mile at the pace on their shirt. If so, then the subject passes the test and they can keep their shirt. In addition, a new stripe magically appears on the sleeve to indicate they have passed the rigorous QA process. If they don't pass, however...