IMO, dont believe the guys that work at autobarn, but also be skepical of what peaple say here. You'll have no problem finding all the info you need to with a Google search.
BPR5ES-11: the 11 refers to 1.1mm plug gap, which is stock gap. If you're running stock boost and the coilpacks are in good condition running 1.1 is obviously fine.
BCPR6ES: notice that the heat range is now 6 instead of 5? A higher number means the spark plug will run colder
Too cold = more chance that it will foul & missfire
Too hot = more chance that you'll get pre-ignition and lower plug life
Usually the more power you meke the colder the plug you require (as more power = more heat), but the tune is critcally important.
The more boost you run the smaller the plug gap needs to be (or the more powerful the ignition system needs to be), as the more dense the fuel/air mix is, the harder it is for the spark to jump the gap.