I just bought my beetle a month ago. It ran fine but had very bad exhaust. So I put a eBay 3 inch kit on it from the turbo back and a new Bosch O2 sensor upstream. Changed the oil (mobile 1) Ngk spark plugs and a new air filter. now after putting a spacer on the downstream sensor I no longer get the catalyst code PO420 , however going down the expressway around 3000 RPM I go into a soft limp mode. I can clear the codes with my scanner and it snaps out of it for about half the day. I changed out the diverter valve but that didn't change anything. The N75 ohm's out ok as well and all the hoses seem to be in good shape. Any other thoughts I'm going nuts.