2005 Acura TL with valve rattle

I bought a 2005 Acura TL back in October 2005. From the time I picked up the vehicle, the engine always ran rough until it warmed up. It clattered something terrible in the mornings. I attributed to the thin oil and the car not being broke in yet. As I had gotten several hundred miles on it, the engine sounded the valves were justing floating and knocking. Kind of like the pistons didnt have quite enough clearance on the compression stroke possibly some carbon build-up or a weak oil pump. It was very obvious from

1700 to 2300 RPMS. The noise persisted everday anytime I drove the car. It sounded like an old Honda whose internals parts were just wore out. It maintained good acceleration and passing power. I never dogged the car once during the break-in period. I had taken it to two dealerships and had many a tech ride with me and they couldn't not hear the noise and I was very atuned to it. It started driving me nuts. I didn't pay $37,000 for a car to sound like it had 70,000 plus miles. The technicians said continue to drive it. If the engine ceases or fails, Acura will replace it no questions asked. I finally got disgusted and called the dealership. They gave me a very good trade for my TL and put me in an MDX. I love the vehicle and the room and have more power than the TL. Guys, give me your thoughts on this engine issue. I had owned a previous 2005 before this one (I wanted the new 2005 because I wanted NAV) and purred like a kitten and ran flawlessly every morning with no ping, knock or anything. Maybe this was just a bad engine waiting to fail -- without my ownership.