I have heard conflicting things concerning exhaust leaks near O2 sensor sucking oxygen to throw off readings. I'm having problems with my 90 (see earlier post L98 runs bad in closed loop). I have headers, and the exhaust has a few small leaks where the pipes are clamped. Is this enough to make it backfire and run terrible when it goes into closed loop? I will probably replace the sensor with a heater sensor. What car should I get one for? I read that the ECM uses input from all the sensors except the O2 sensor and the Temp sensor in open loop, then uses feedback from the O2 sensor after it goes closed. If this is true, them all my other sensors must be ok, leaving the O2 sensor. I just got an ALDL cable th use Datamaster, will try it tommorrow.