I don't own a lambo, and I never have, but I have had experience in breaking in high performance motorcycle engines. With those it is important to vary the engine rpm often while staying below the specified limit. Especially while driving on highways. "engine braking" helps in seating the rings (meaning allow the engine come up to operating temperature and then accelerate to the given limit and then immediately let off the gas and allow the motor to slow the vehicle down). Fluctuating the rpm up and down during the entire break in process always yields a stronger motor after the break in is done. Maintaining a constant rpm isnt exactly harmful, it just won't be as strong of a motor as one done the way I described.