Andy - I had an brand new inlet manifold on mine, I actually saw it and there were about 2 and 1/2 flaps missing! plus looked all knackered one end...it made no difference what so ever, they did a smoke test and it was leaking for sure but the car and DPF issues were still there, I really do feel for you mate as remember so many times thinking I just want it sorted.
Glen - I believe this is pretty much what Max had happen, maybe you can confirm Max? but if the car was fine before they got their stinking hands on it then I would put it all back on them to sor! Its good Audi UK were helpful, when ever I had spoken to them or VW UK they had been great in giving me information about cars I was thinking of buying and their history, but as soon as I spoke to them about the plethora of faults mine had it was...goodbye n bugger ya!