I recently bought a used RNS-E unit for my 2008 TT. I would like to have a VAG-COM tool when I install it. I see a bunch of these listed on eBay, but I don't know whether they're going to work. Can someonw please tell me what tool/software I need? I saw one listed at Ross Tech for $349 + $99 for software. Is there an alternative? Thanks.