Temperature different of adapter since Mountain Lion (maybe only rMBP related)
That's interesting, I a have been running a non-Retina i7 for over a year, Lion OSX, and have found that CPU and GPU get drastically throttled as MagSafe-1 gets hotter and hotter. Nothing unusual I guess but I didn't expect it to impact the performance of the machine.
I may just upgrade to Mountain Lion, hopefully that will fix the throttling!