Here is my anecdotal evidence on the matter:
14k miles on the odometer, my engine is tuned
17k miles on the odometer, first coil pack fails and is replaced with an OEM part
20k miles on the odometer, second coil pack fails in a different cylinder and is replaced with an OEM part
21k miles on the odometer, I get tired of limping the car home and replace the OEM coil packs with R8 coil packs
40k miles on the odometer, I changed the spark plugs
51k miles on the odometer, I am at today with no further coil pack issues.
My personal observations, while true, do not prove anything. However, a trend starts to take place when my anecdotal evidence is combined with many other individuals on this board who have had similar observations where they too switched to R8's and have suffered no further coil pack failures on their engines. As others have stated this is only a trend based on a collection of anecdotal observations and not proof of a theory as to why. I am not sure we will ever know the answer as to why there are many observations of people having improved coil pack reliability on their tuned cars when switching to R8's. That said, the experiences of this forums' users would also suggest one carry extra coil packs in their trunk if they are tuned and not running R8's.