Its an Audi. Take it to a dealer. It could be your ECM, your blow off valve on a turbo system designed without one, bad turbo, it could be any nmber of things. Audis are a pain in the ass, and tuning them is even more of a pain in the ass. I have had some FUCKED up cars come in the dealership that have been to Eurotech. I would put the stock turbo recirc valve back on and take it to a dealer.