When fully warmed up mine fluctuates between 14.7 and 14.5 .
Thanks15.2 sounds about right, it's not a million miles off what it should be. fwiw I have emanage blue and the AEM UEGO wideband and my AFR at idle pings around from low 14's to high 15's.
No you are correct.It should dither any thing from 2 to 3 times a second up to about 6 seconds either side of the value indicated. The value should as others have said be around stoich 14.7. If yout get an exceptionally slow dither or no dither it is a sign the your O2 (narrwoband) is past its best.