Hello Alan,
....coming back to Your 3 yrs old advice on how to connect the gauge/controller cables of the MTX-L device : what´s about the BROWN cable ( cable No.5 ) ? Did You reconnect it to the cable of the original O2 - sensor ? And did You You completely remove or disconnect the 2nd O2-sensor ( means the post-CAT ) ?? Would You pls. share such details ?? Thanks in advance_Lutz