Audi Q5 Pull Back/Surge/Shudder after 120kph

[Audi Power-SA]

I am a new member from the beautiful South Africa, and firstly would like to say Hi to everyone

I have a 2009 Audi Q5 3.0TDI, 7 speed s-tronic gearbox, and have been having a problem when driving 120kph and above, especially on uphills, where the car would give a pull back/surge/Shudder every now and again...Sorry this is the best I could explain the problem...I tried changing it to manual but still get the same problem. Audi have had my car for over 6 months, they have changed the gearbox, engine mountings, tyres, oil, oil filter, fuel filter, ecu mappings changes, changed diesel suppliers, used diesel 50ppm & 10ppm, used diesel cleaners, no faults reported on the system even when driving with the laptop plugged in and the problem surfaces...Is there anyone that has had similar problems, or can guide me on what the problem could be as it looks as though Audi is running out of ideas on what the problem could be?