Veggie can also cause sticking Piston Rings which can cause low compression which can cause hard starting.
If you live in the USA you can get a compression testing kit from Harbor Freight stores for $30 or so and less when it is on sale.
To improve your starting you could update your Loop/Filiment type Glow Plugs to the Pencil type if you do not already have them installed.
If it turns out your compression is low you might try Pulling the Inectors or Glow Plugs and pouring in some Marvel Mystrey Oil and letting it soak for a week or so. (Afterwards do an Oil Change.)
Or some have claimed changing to Synthetic Oil over the course of several hundred miles will free the Piston Rings.
Something all off the above should be here:
DIY Repair Links
http://www.peachparts.com/shopforum/forumdisplay.php?f=82
http://www.peachparts.com/Wikka/DoItYourSelf
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