We're now at about the same level of development of DPFs as we were for catalytic converters in 1997. Many of the first generation were disastrous. But engine and DPF development has taken place since. Best to avoid old tech diesel engines that were never originally developed for DPFs. And preferably go for one with the exhaust manifold incorporated into the cylinder head as that is bound to be more effective because the DPF heats up more directly. (Mazda 2.2 Skyactiv, Renault 1.6DCI, Vauxhall/Opel 1.6CDTI.) To achieve EU6, most diesels (apart from Mazda’s Skyactiv) require an expensive additive called ‘AdBlue’.