It might just be my imagination. I have noticed this over the last couple of years owning my truck. After parking my truck for a couple of hours I crank it up and and head down the road, I have incredible throttle response and perfect tranny shifting. The engine temp is a little over the the 160 mark. As the truck warms up to and past 185 range, I get less throttle response and the tranny shifting is less smooth. Granted it still has great power, but not near what it is right after the truck sits for a couple of hours. It seems like the power degenerates a little the longer I am driving. If I stop, park, and do my business for a couple of hours and get back in, the truck is balls to the walls for a little while and then the power seems to back off some. Also (still could be my imagination) the truck seems to run quieter and smoother at night versus during the day. Is this just a characteristic of a diesel engine or do I have some kind of hidden issue. Has anyone else experienced this?