i c/p from looking in less than 1 minute from AEM forums this test;
pull the sensor out of the exhaust stream. Key on engine off,
what does the gauge read? (it should read full lean ---)
Next get a rag, spray the rag with a bit of brake cleaner. Then cover the
sensor with the rag, what does the gauge read? (It should read full rich
If the gauge does not indicate as expected the problem is likely
with the wideband sensor itself. If the gauge does indicate as expected the
problem may be related to your exhaust or the placement of the sensor.
have you looked through their forums?
89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.