My boss keeps telling me that people on his VW forums talk down on the udp because it can "unbalance" your engine. He has cited some interesting points and I was wondering if anyone had encountered "sonic resonance" or any kind of issues at all while using a udp on our cars. Honestly, I noticed a nice gain on throttle response with very little trade-off. I have a couple of thousand miles with it on an the car runs great, maybe VW engines are just cheaply made (wink)