Just to reply to Bassam Asif. My car is in with the exact same issues. The DPF is clogged because it hasn't done a regen in 19,000 miles..(I only have the bar 4 months.) They have no clue what caused it.
Audi want me to buy a new DPF..but I want to fix the problem causing the issue regens to stop. Then clean out the DPF and see how I get on. If anyone has any thoughts?