Yet another Mitsubishi engine with the same symptoms. This one is in a Clark that has just over 2000 original hours.
1. Engine does not smoke when first starting which indicates that the valve seals are good
2. Engine does not smoke when using the truck in a normal driving situation.
3. Engine does not smoke when running it hard.
4. As in all of these cases, the only time the engine smokes is when is sits idling for five minutes or more. It will blow smoke for a minute and then clear up.

As always, any help or insight will be greatly appreciated.