Just received this info from Fergus regarding the testing for his diesel Tiger.‘ Totally standard lombardini LDW1003, tier 2 emissions engine. The exhaust is straight through stainless. I think the point is that since the engine only revs up to 3,800 rpm, the NOx levels don't change much from idling, so the average is 0.08 g/km, which is euro 6 standard. If the engine was turbo charged, it would most likely fail.
It was tested at the rolling road ULEZ facility in East London.’
So there you have it