Yeah, if you hear the drive radio "I need more power give me more power" the teams will allow the drivers to change engine modes or restrict them from doing so to protect the overall life of the engine. Drivers can change modes for the engine to run lean, which will help conserve fuel but lose a little power output. Or "I need more power", they can run more rich, which uses more fuel, which in turn cools the engine a little more, and gives it more power, but will shorten the engine life. I believe they are restricted from racing in qualy mode though.