I had 407 1.6hdi, and I know there is no way to be compliant without DPF as that was a very common practice where I came from. Once that person goes to Germany or, even worse, Austria, they can be sent to testing by traffic police if there is suspicion that DPF is removed, and they could NEVER be in compliance. I sold my 525d E60 bcs. At 475,000km I had to replace DPF and since my brother and I used the vehicle a lot in EU, we really did not want to invest in a new DPF in a car that has pretty much half a million km. So, we just replaced it with a new car.Eyeballing is only the soot coming out of the tailpipe. The aforementioned parameters were measured with the appropriate tools in a licensed for the job garage. It was supposed to comply with Euro 4 standards with all the components in place and it still did with no issues without them.