Well, I am still battling the emissions problem that I surfaced a few weeks ago, having failed smog four times now. The last time I was very close, in Texas we have a 15mph and a 25mph test and I only failed Nox on one of them, having fixed an air leak, dropped the dirty oil, my shop replaced a sensor on the intake, and we put a paper filter in the airbox instead of the K&N. So the next most appropriat thing was to install a new catalytic converter. I bought one and had it installed a couple days ago by a muffler shop that had done work for me before, the same day the Check Engine light came on. My shop looked at the code and the Oxygen Sensor is likely bad. The muffler shop advised me to drive it on the highway for 20 miles to "break in" the new cat, I have done this. How the Oxygen Sensor failed when being swapped may be misinstallation, on the other hand the car has 97,000 miles on it and they appear to last about 100K, so I am okay to replace it. FCP Groton has them for this Rex Regina car, anyone done this before? Is a special tool absolutely necessary when putting the new one in? I checked the FAQs but could not come with anything directly applicable. And the archive doesn't really show much, either. HELP!