I am quite late on this thread, although I read with interest having had the full DPF removal, straight through pipe, remap, etc; applied to my 57 plate 159, 3 years ago.
Whilst the legislation is obviously yet to be clarified, is it likely that it will be retrospectively applied to vehicles manufactured before date that the new rules come into play? Taking the example of emissions, whilst Euro V emmissions standards are in effect (with Euro VI on the way....??) - my 57 plate is only required to satisfy Euro IV standards as those were the regs that applied at the date of vehicle registration. (Incidentally, it meets Euro V regs in any case).
Is it being suggested that DPF on = Pass, DPF off = Fail, criteria may end up being applied to all commercial diesels, regardless of year of manufacture? (Although am I correct in assuming that vehicles registered after Sept 2010 are mandated to have a DPF fitted?)