I think I'm encountering the same thing. Not necessarily a power loss, but power inconsistency. One time on one cooler day (in fourth gear), I could actually feel some kind of boost flutter where it didn't seem to know how much to put down. It pulled hard, then eased, the pulled hard again, then easied, in rapid succession. Then on another day it made me wince it was shoving so hard in the same gear....I don't get it. I think it has everything to do with boost.
I also notice it doesnt sound like its working very hard when the output seems low.
