I've noticed it a few times while entering expressway ramps.
One time I floored the gas pedal to see if it would stop but the studder continued, I let off at 4500rpm in 3rd because I only had 500 miles on the car.
Lately, approaching 1,000 miles on the car, I've begun to run it a little harder, and most of the time there is no studder.
I wonder if it is an ignition/electrical problem, it makes the car feel like it needs a tune-up, but since this is a new car, obviously it does not.
I also wonder if gutting the up-pipe will solve the issue.