Sprinter '07 311 CDI 2.1litre. First symptom - black smoke on start-up in cold weather. No error codes. Smoke cleared quickly as engine temperature rise. Second symptom: failure to start at all one frosty morning. Started with smoke at lunch time. Took it to Mercedes dealership. They couldn't find a problem, said it started fine, but renewed glow tubes and relay, said if not this system, then must be injectors which they wouldn't touch as these had been refurbished and reinstalled about 6 months previously by an independent. Took it to another independent injector specialist, Bosh agent. Leakdown test OK although lower pressure on both low pressure pump and high pressure pump. They also noticed DPF had been removed (by previous injector refurbishers without my approval after my complaint at loss of power - I subsequently found that wrong codes for injectors had been applied and I had to get Mercedes dealers to recode), but that start up smoke was too much to attribute solely to this. They suggested returning it to original injector refurbishers as injectors were still under 1 year warranty. They also said change battery as seems tired. I DIY charged battery, 12.48 volts on reinstalling, 14.4 volts on idling, 11.7 volts on ignition (first position) and lights on but not yet cranking motor; so thought not battery, maybe starting motor tired but not cause of smoke issue. Third symptom: EGR error code now displaying P0404 - performance, range issues. I DIY removed and cleaned EGR, coated with soot but mechanically seemingly OK. Erased code and took van to previous injector overhaulers . Code reappeared. Smoke now appearing on cold starts throughout the day, not precisely on initial starting but on subsequent gentle revs, engine rough to begin, then settles down, limp home mode comes on after 5 mins driving. Multicoloured black and grey smoke on start up revs now. Injector refurbishers say EGR failure only to blame - I think this is maybe a secondary symptom, not primary cause. I think maybe injector failure, maybe removal of DPF has reduced back pressure on cylinders, maybe reprogramming of ECU to void DPF sensor input has led to problems. What do you guys think?