I've heard there is a difference in accuracy based on the sensor's location. What kind of differences have you guys seen? I know the optimal location, but when tuning friends cars I will be using my tailpipe sniffer... Don't want to blow any engines

 

Assuming he does not have a cat(other pets are O'k ), there will be a small RPM lag, readings should be the same so long as the sensor is well up the pipe.

 

Thanks!

 

And no exhaust leaks.