i had mine done under warranty on my last car ('07) when it had 74k. they replaced both wastegates under warranty with no issues or hassles. the car had 125k on it when i traded it in and the problem never came back.
my '08 is not showing this issue...finger's crossed. i just picked up the '08 yesterday so i'm going to take it to Maranello ASAP for an inspection before the warranty expires.
'88 Porsche 944 - SOLD
'90 Audi Coupe Quattro - SOLD
'07 E90 335i 6MT - SOLD
'08 E90 335i 6MT - SOLD
'13 BRZ SportTech 6MT - current