Diesel Purge is one of the few worthwhile aditives or treatments. I used it on my 85 300D. Although the best way to use it is to feed it through directly, like you mention, it can also just be dumped in the fuel tank if you have any left over.
I would also suggest you check out Rusty Cullens for a supplier at
www.buymbparts.com . I'm pretty sure he sells diesel purge. He also has outstanding prices and service.
And
Performance Products sells diesel purge, although for a higher price than Rusty. They have nice catalogs, though, with lots of exploded drawings of engines and bodies. I find their catalog to be a useful reference.
Benzaholic