I was reading my Haynes manual and read the procedure for breaking in a new or rebuilt engine (for the Xterra, Frontier etc). It advised driving the truck in an open area and accelerating from 30 to 50 MPH and then letting the vehicle rapidly slow to 30 MPH (I am guessing using engine braking) to seat the pistons. This is to be repeated 10-12 times consecutively. The vehicle should then be driven gently for the next couple of hundred miles with an oil/filter change at 500-600 miles. Haynes then suggests driving the truck neither aggresively nor gently for the next few hundred miles. They consider the engine broken in at approx 2000 miles. That is the most comprehensive "break in" information I've read so far. What have YOU done?