Looking for some more help and advice. I've had a load of problems with my car over the past few months, and all of them have been fixed now. But I have these persistent little things that my garage are either unable (or maybe unwilling:P) to fix. Note; the car is under warranty and garage have been carrying out repairs free of charge so far!

Car is a 2007 Audi A6 2.0TDI S-Line Auto, approx. 80k on the clock.

1. The car idles quite badly, but not all the time. It happens on almost every journey, but not every time the car is stationary. The rev needle bounces up and down between approx 850-1000 rpm, the car noticably shakes, MPG read out starts dropping and the car smokes a bit (and i usually notice a diesel smell while it's doing this). This problem comes and goes.

2. It revs too high when driving at low speed. It's like it hangs on to a gear too long, so it revs at around 1300-400rpm at 20mph and stays at this rev speed while I'm slowing down, then the revs suddenly drop to normal when the car is almost at a complete stop. Same as above, this problem also comes and goes.

3. The car judders at low speed with low revs. For example, if I'm driving at around 20-25mph on a flat and clear road, with revs around 1100rpm and I'm barely touching the accellerator... Just maintaing that speed with very gentle throttle. In this situation the car starts jerking and juddering... it almost feels like i'm tapping my foot on and off the accelerator in too high a gear. If I put my foot down a bit it responds and is fine, it only seems to be low speed/low power/low revs situations that it does this.

The car has had so much work done to it, and so much replaced (see list below) that I'm really keen on keeping hold of it now. But it seems like my garage are at the point of giving up on it and I'm after any advice or info on what could possibly be causing it. From a few hours of Googling and reading, I've come across some suggestions already:

Change gearbox fluid and filter.
Remove and clean wheel speed sensors.
Check torsion values.
Check idle stabilisation valve.
Check/clean throttle body.
Unplug battery and reconnect to allow throttle body re-alignment.
EGR valve fault
Software and EGR (Apparently a software update is available to stabilize the idle and reduce egr flow to prevent the EGR allowing to much flow which results in a judder)

What I'd like to know is; in anyones experience are these things likely to resolve the problem? What would be the best order to tackle this list in, and is there anything else worth considering?

This is whats been done on the car so far that's worth mentioning:
• New/Remanufactured Engine fitted
• All injectors removed and sent away for full testing. All OK.
• Injector seals replaced.
• Injector wiring loom replaced
• Dual mass flywheel replaced (and, I’m told the Torque Converter too)
• Oil sump removed, cleaned sump and pickup
• New oil pump
• New lambda sensor
• New oil pressure sensor
• New MAP sensor
• Vacuum hoses check and inspected
• New fuel filter
• New air con pump
• Cambelt kit and water pump
• Full service

The car has recently been to Audi main dealer who wanted a load of hours and bags of money to start fully investigating loads of things, including repeating things that my garage have already checked.

Sorry for the massive post, got a bit carried away! This problem is doing my head in. It's a real shame too, because apart from idling and these low rev/low speed issues, the car drives beautifully. Sometimes feels like a brand new car!