Seriously check VWvortex, they have an airride forum and it will answer a ton of questions for you. I know most people are dealing with Airassisted and Mason tech for their setups and most people are using a variety of different pumps, controllers, tank sizes, line sizes etc. Most "kits" are overpriced (round $2700+) but if you do your research you can piece it together for 1/2 that... but just a warning to slam the car you better be willing to notch the frame up front to clear the axles...if not, you'll only go as low as coilovers in most cases! Good luck