I added rear air suspension to my 2014 VW Touareg to improve its towing capability. Air springs, compressor and solenoid valve bank came off a 2011 Porsche Cayenne. I used a Siemens Logo PLC to measure ride height and automatically adjust the rear suspension to maintain level when we tow our travel trailer. The Cayenne shocks are also electronically adjustable, which really helps keep the vehicle from bouncing when we tow. The TDI Touareg has great towing ability (7700lbs), but with coil springs and VW stating a weight distribution hitch cannot be used, the rear suspension sags really bad. Air suspension is the ideal solution, unfortunately the Touareg was never sold in the USA with air suspension. Here's how I added it to mine.