I recently found a video that was done by Mike Reagan when he was still with Lionel. He shows how to improve the smoke output on a steam engine, but I guess it also applies to diesels.
I decided to make the modification last week on 2 of my engines that had poor smoke production. WOW, what a difference. The flow is much better and since one of the engines is a Legacy, I am able to control the smoke flow from low to medium to high.
If you haven's seen this mod, perhaps you might want to give it a try. It was very simple, took less than 15 minutes to complete.
I do suggest that once you do it, run the engine without the shell to insure that everything is working correctly.
Below is a link to the video.
RAY