fitted my afr today.
results suggest urs is either lean or naff landa.
mine fluctuates on idle, runs rich on acceleration and leans right off under deceleration.
however fitted to my old mi16 it really played up doing what yrs is doing.
droped right off the scale on deceleration and only went rich on WOT.
rolling road tune mite find ur problem but im not too familular with the engine yet so my advice is go with what john A says... he seems to be "the daddy" with the C20LET.