I have mine in the exhaust pipe(street car) just after the collector on the full exhaust and another set in the colletor extensions for at the track testing with open headers, no difference in readings between the two I started out with a LM1 and then bought a FAST system with the dual wide band reading, I have since bought the LC1 upgrade for the LM1 do to its data logging and transferring ability which the FAST system does not have Thank twice and avoid buying twice