update on today progress, koracing, following your pointers, traced and found there is no wire in #37 in my miata, so I tested #50 assigned Aux3 in tacho setting, then switch the wire to #37 slot and managed to get it work, with a setting on HIGH side.
Vaughan diagram is applicable to this 95' 1.8L Miata, no B/W wire on #37.
Thank you very much, koracing and Vaughn for sharing the useful diagrams and valuable pointers.
I'll work on the CEL next and noted on the knock sensor pull up.