Raw fuel out the tail pipe as in liquid amounts?  That would sound like an injector or injection pump failure to me....has the pump and injector been pulled and tested?
Also...keep in mind no matter what prep is done to run WVO, they weren't intended to from the factory, so in the long-term use of it, something could possibly go wrong as a result. 197k miles is unusually low for failure of an OM606....they tend to go a long long time....often further than even the 616 and 617's do.
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-diesel is not just a fuel, its a way of life- 
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)
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