I have been reading a lot of the posts about emissions test failing etc. and have not been able to resolve my wagon's problem. I started out here in Ontario failing a test that showed high NO2 and very passable HC and O2. So I replaced the O2 sensor with a universal one (2 heater wire - 1 power wire). It went in fine. Took it back in and got basically the same test results - high Nox, low everything else. Next I replaced the Cat Converter with another universal model and it too went in fine. Took the car in with supreme confidence and this time failed in a very weird way. The Nox is now very passable and the O2 and HC are approx. 13x above what they should be! Basically the test place said black smoke was coming out of the tailpipe as if it was burning raw fuel. My friend and I are very careful when doing the work and we did have a torch going to weld the cat converter, but I don't think we have damaged the O2. 3 months ago I replaced the plugs, wires, cap, rotor, oil and air filter and did a tune-up. Runs like a champ except for this. 308k. Any help would be greatly appreciated as I'm going nuts trying to get this thing to pass.