Ha ha - guys you are all wrong... the explanation is very simple:
I am not sure about D3/D4 but when it comes to 3L not all 1,2 are 3L in Germany - only cars without Servo and Climatronic are 3L!
ALL 1,2's meet the demands of EU4 but EU4 did not exist in 2001 so all A2's from 2001 are certified as EU3 accoirding to COC - but - at least in Sweden you can reregister your car in EU4 if you have original COC.
When it comes to 1,4 TDI 75HP it's a little different - 1,4 TDI did not meet EU4 until 2004 when the engine was changed.
All 1,4 TDI 90HP are all EU4 certified.
When it comes to cars wheight - all 1,2TDI are about 160kg lighter then 1,4 TDI. Some of the components that are lighter are:
wheels made of magnesium alloy,
steering wheel,
lighter components on front and back axles,
lighter front chairs,
less isolation,
thiner windows............
1,2 with no servo and clima wheigths about 830 kg - with servo and klima ca 860 kg.
