I am getting an intermitant cel light for my highflow cat and might do the spcer mod but want to make sure it wont affect any readings with the ECU.

 

that o2 sensor only tells the ecu if the cat is working. If you get a spacer, it will make the o2 tell the ecu that it is

 

Thanks I had heard that it might change some air/fuel readings.

 

The first O2 (pre-cat) is used to measure combustion efficiency (lean/rich) and make adjustments. The second O2 (post-cat) is ONLY a CAT-Health-meter, as cincyTT says.

 

cool thanks

 

They are right the 2nd is more of a "tattle tell". I was running my 3" hi-flow cat and STILL threw a CEL after a couple of months. Even tho they said it wouldn't. I kept clearing them but consistently would throw a cat below effeciency code. I took out the cat examined it and found no issues, cleaned the sensor but still had issues. I said screw it and threw in the test pipe with an arrestor.....still no luck. Eventually I just ditched the arrestor and attached the sensor to the bung.

I haven't even bothered with replacing the sensor tho...oh well.