emissiin mot failure

[dean.st]

Golf 1.9 tdi bxe pd engine.

It failed the mot on friday with emissions being double what they should be. I fitted a replacement cat pipe and it failed again today as no difference in emissions.

What the hell?

What else can i do? i have put diesel cleaner in the tank and plenty of fresh diesel. the car doesn't smoke either.

There are no modifications to the engine.

[Crasher]

Make sure the air filter is perfect, even fit a K&N as the more air you get in the less smoke. Check the engine for fault codes and the torsion value to see if it is as close to 0 as possible, not 2 or 3 degrees out.