Just installed Arnott bilstein shocks in my 2004 allroad. The fronts went into Arnott air springs. The rears went into the original audi air springs.

Here are a few tips for putting Arnott Bilstein rear shocks into stock Audi bags that Arnott's instructions don't mention.

1) You have to unbolt the lower control arm from the brake/wheel hub to get enough clearance to remove and reinstall the airspring/shock assembly. This bolt is at the outer end of the lower control arm. It holds the rear wheel alignment position. It has a concentric washer attached to the bolt head and a keyway on the nut end that another concentric washer keys into. Before unbolting this alignment bolt, be sure to carefully mark where that bolt and keyway are lined up with the lower control arm (so you don't lose the alignment setting). And turn the nut, not the bolt head, to loosen it, removing the nut before carefully tapping the bolt out with a punch (so you don't damage the end of the threads).

With the lower control arm unbolted at the wheel end, a pry bar can be inserted into it and it can be pushed down enough to clear the bottom of the shock from the control arm to remove the shock/air spring assembly. I had a neighbor help, but it could be done alone by stepping on the pry bar. A 2 foot pry bar worked well. A longer pry bar may need to be slid up through the control arm to make sure it doesn't hit the ground before you've gotten enough clearance from the control arm.

2) Arnott's instructions called for using a spacer when putting the shock into the Audi air spring (not required for the Arnott air spring), but it wasn't in the package from Arnott. A call to Arnott revealed that the spacer is no longer needed, but they haven't updated their instructions.

3) Reinstalling the assembly with the new Bilstein is near impossible because when the assembly is under the wheel well, there's no way to get enough leverage to compress the shock so it will fit up over the lower control arm. TRICK - After the shock is installed in the air spring, have a friend compress the shock by standing it up on the ground and pressing straight down on it with all his weight. Standing above it and pushing straight down on the assembly was the only way I could get enough leverage to compress the shock. While it's compressed, use a daisy chain of plastic zip ties to hold it in the compressed position. (I suppose baling wire would also work.) Run the zip ties through the bolt hole at the bottom of the shock and through the two upper mounting holes on the air spring top bracket. Pull them tight to hold the compressed position.

Then bring the compressed assembly to the car and with one person pushing the lower control arm down with the pry bar and at the same time pulling up on the wheel hub assembly, have the other person feed the assembly up and into place. Be sure you have the right air spring on the right side and the left air spring on the left side. The two threaded holes where the air lines screw into the spring go to the front of the car, away from the axle. You could do it with one person stepping down on the pry bar, but two is easier. If your pry bar is too long, it will hit the ground before you've gotten the control arm far enough out of the way. You can slide a longer pry bar up through the control arm if necessary.

With the spring/shock assembly in place (and on the correct side of the car with the air hose holes to the front of the car), cut the plastic ties. I put a pry bar under the shock, between the shock and the control arm, to keep it a bit above the control arm while I removed the tie from the lower shock bolt hole. Otherwise the plastic tie gets wedged between the shock and the control arm and you've got to pry the shock up to free the plastic and get it out of there.

3) The bilstein shocks do not have a clip for holding the air line to the shock (as the original Sachs shocks had). I used a plastic zip tie through the small hole in the inner side of the control arm just under the axle to secure the air hose away from the axle.

4) Arnott tech folks are awesome. If you have trouble, call Arnott.

5) Arnott provides plastic plugs for the extra air hole in the Audi air spring, that the bilstiens don't use. Arnott's instructions were clear on this, but be sure not to lose the two plugs.

Hope that's helpful.