I do them all the time, I drop the subframe assembly, steering and all, completely out of the car. Super easy, then you have much more room. Still can be tricky to get that band clamp back lined up going back together.
Between CR TDI DPFs and EA888 blown rear main seals, there is hardly a week that goes by that I do not have the subframe out of some A5 car... two so far this week, and it is only Wednesday.
A quick guide:
Lift the car, making sure you have plenty of room underneath and the car is level.
Disconnect the battery.
From inside the car, make sure the steering wheel is straight ahead, remove the lower steering shaft cover by the pedals.
Remove the steering shaft bolt to pinion, slide the shaft up and off, let it hang, make sure the steering wheel stays straight(ish)
Remove the airbox, battery, battery tray.
Remove the electric steering harness (ground is at ground lug on body, shared with ground strap to trans, power is at fuse link box, communication connector in a clip near backside of headlight)
Unclip the harness, feed it back and stuff it down in the hole between the trans and firewall (this will come down with subframe).
Remove front wheels, lower splash shield, and side shields (NCS/NMS cars, the whole fender liner comes out as they are all one piece).
Remove the sway bar links' upper attachment points to struts.
Remove tie rod end attachment points to knuckles.
Remove exhaust hanger bolts at rear of subframe, and roll mount bolts at transmission.
Support the subframe, remove the six big bolts that hold it to the body and lower it down (note their locations, as some cars use different bolts/lengths in different spots).
Be sure to watch the harness you removed from above so that it doesn't get hung up on anything on the way down.
Remove the right (long) axle heat shield from engine block.
Remove inner CV joint from right axle from transmission and turn the knuckle/swing the axle back and out of the way, secure it however you like (you needn't remove the outer joint bolt).
^^^I usually have this done inside of 30 minutes^^^ Sometimes the upper links' nuts won't come loose, and I have to cut them off and replace the links... these commonly wear anyway, and are cheap.
The DPF:
Unplug both the EGR and DPF pressure sensors (the EGR one is protected by a little space blanket).
Remove the Torx bolt for each (DPF one is the easily seen black one, the EGR one is a backside one going into the valve cover).
Remove the smaller of the two hoses from the EGR sensor (the one on the valve cover).
Both sensors will come out with the remaining hoses attached with the DPF.
Find the wires for the two temp sensors and oxygen sensor at the top of the DPF, follow them over to their connectors in the bracket near the brake master cylinder, disconnect all them, and feed them over towards the passenger side.... these also will all come out with the DPF.
Note: one wire comes in with these at a bracket towards the back of the turbo, this is NOT getting removed, so make sure that wire stays in place.
Remove the three nuts from the upper heat shield, and pull the heat shield off (it'll be a squeeze).
Under where the DPF pressure sensor hoses make the bend, sort of between the DPF and engine, is a single bolt, that is a mounting bolt, remove it.
Go under the car: remove the right plastic underbody shield, then find and unplug the orange connector for the lower EGT sensor, and fish the wire out of its clips in the heat shield. This sensor will also come out with the assembly.
Remove the low pressure EGR tube (two bolts to the EGR cooler, one tiny V-band clamp to DPF).
Remove the V-band clamp at back end, where it attaches to the deNox catalyst.
Loosen V-band clamp at turbo.
Remove lower DPF bracket (two upper nuts, two lower nuts).
Work the DPF off of the turbo with a couple twists, then carefully lower it out the bottom of the car, taking care that all your wires, hoses, and sensors are all coming with you and not getting tangled or caught on anything.
Now you have to swap over the sensors, and the one pipe, from the old DPF to the new DPF. This can be a pain, and it all has to fit exactly, so pay attention, take pictures as to the sensors' orientation.
Tip on V-band clamps: you often have to loosen the bolt, swing it completely out of the way, then tap each segment off of the exhaust to get them loose. They can be a pain. There is also a steel gasket in there, note its position.
Plan on just getting all new clamps, gaskets, and maybe that upper mount bolt.
Going back together, make sure the DPF is fit properly to the turbo before completely tightening down the mounting fasteners. Then, going back and forth, tighten that V-band clamp down. If you do not do it right, you'll have an exhaust leak.
Once you get the car all back together, you need to reset the DPF with VCDS or similar. Let the car know it has a new one, login, adaptation, etc.