Thanks! Due to all the extra emissions crap on the TDI I'd have to get the ECU reprogrammed by a tuner after removing all the other stuff in order to keep it running right. Just adding an O2 sensor would be nice. I was more concerned with how thorough they'd be (then I remembered how they do the gasoline emissions check...just check for codes like you said) and worried that for some reason they'd notice the missing cat. I tend to be a worst case scenario kinda guy when it comes to bureaucracy. With my luck I'd somehow get flagged and have to replace everything Nice! Shit! Good luck with the rebuild. That's another thing that worries me about stepping up the output of the VW. I don't think that the modest gains I'd see would do anything that drastic, but I still wonder about long term reliability.