This has become a hot topic lately, a few people have ordered or are about to order an upgraded rear arb and many more are asking about it so I reckon it would be helpful to have this information gathered in one thread, instead of scattered in various (sometimes not even related) threads. Information about possible options, installation and reviews of-course. I've went for the H&R 25mm one, the model number for the 2.0T 272/280 AWD cars is: 33581 HA5.  The model number for the 2.0T